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Smoothing serums vs. growth serums: This article covers styling serums for frizz control, shine, and smoothness. If you are dealing with thinning or shedding, see the separate guide to best hair growth serums on Amazon -- those work at the scalp level and do a completely different job. The products here are applied to the lengths and ends after washing to smooth the cuticle and control frizz during and after styling.
What Makes a Good Smoothing Serum
The core job of a smoothing serum is cuticle management. The cuticle is the outermost layer of the hair shaft -- a series of overlapping scales that, when flat, give hair its shine and smoothness. When those scales are raised (from humidity, heat damage, or mechanical friction), moisture gets in and the strand swells unevenly, creating frizz. Serums work by physically flattening those scales and coating the shaft to prevent moisture entry.
- Silicones (dimethicone, cyclomethicone, amodimethicone): The main workhorses in most serums. They lay flat on the hair shaft, seal the cuticle, and create the slip that makes hair feel smooth. Amodimethicone is particularly useful because it deposits selectively on damaged areas where it is most needed.
- Argan oil: A lightweight lipid that penetrates the hair shaft as well as coating it. Adds shine without the heavy feel of thicker oils. The ingredient that made Moroccanoil the gold standard.
- Keratin: A protein that temporarily fills gaps in the cuticle from heat or chemical damage. Especially effective for coarse or chemically treated hair that needs structural repair alongside smoothing.
- Silk proteins: Film-forming proteins that smooth the cuticle and reduce friction between strands. BioSilk built an entire product line on this ingredient.
- Botanical oils (marula, jojoba, coconut): Lightweight carrier oils that add shine and some moisture without silicone heaviness. Better for fine hair types that react poorly to heavy silicones.
What to avoid: heavy mineral oils or petrolatum in a serum (these coat without conditioning and cause buildup over time), alcohol-heavy formulas that dry out the hair shaft, and anything marketed as a "serum" that is really just a leave-in conditioner without any smoothing agents. Also keep in mind that for daily heat styling above 350 degrees F, serums are not a substitute for a dedicated heat protectant.
The 7 Best Hair Serums on Amazon
Moroccanoil Treatment
Moroccanoil Treatment is the product that made argan oil a household name in hair care, and it has held the top spot in smoothing serums for over a decade for good reason. The formula combines argan oil with keratin and antioxidants to deliver a two-pronged effect: immediate surface smoothing plus a conditioning benefit that builds with use. The argan oil penetrates the hair shaft rather than just sitting on top, which means you get genuine conditioning alongside the shine and frizz control, not just a surface coating that washes away.
One of the things that distinguishes Moroccanoil from lesser argan oil serums is the finish. It delivers real shine and a sleek, smooth result without the greasy or flat look that heavier oils can cause. It also slightly reduces blow-drying time because the oil helps the hair shaft release moisture more efficiently. The scent is distinctive and pleasant -- worth knowing about if you are sensitive to fragrance in hair products.
- Genuine argan oil + keratin formula
- Reduces drying time noticeably
- Delivers shine without grease
- Builds conditioning benefit over time
- Works on all hair types and textures
- $44 price point is a splurge
- Strong fragrance may not suit everyone
- Easy to over-apply on fine hair
Paul Mitchell Super Skinny Serum
Fine hair has a uniquely unfair relationship with smoothing serums. The products that work on thick or coarse hair -- heavy silicones, layered oils, keratin treatments -- just weigh fine hair down, leaving it limp and flat rather than smooth. Paul Mitchell formulated Super Skinny specifically for this problem. The serum is exceptionally lightweight, with a watery-silicone texture that distributes evenly without any heaviness and dries to a barely-there finish that eliminates frizz without adding any weight to the strand.
The formula also contains a small amount of conditioning agents that improve the hair's overall texture and manageability over time. It works as both a blow-dry prep (apply to damp hair before heat styling to speed up drying and reduce frizz) and a finishing serum on dry hair for flyaway control. For anyone with fine hair who has given up on serums because they always make hair look limp, this is worth trying first.
- Genuinely lightweight -- no heaviness
- Works as both prep and finishing serum
- Eliminates frizz without flattening volume
- Affordable price relative to performance
- Works well under heat tools
- Less shine payoff than heavier serums
- May not be enough for very coarse or thick hair
- Fragrance-forward formula
BioSilk Silk Therapy with Natural Silk Complex
BioSilk's signature ingredient is natural silk -- actual silk proteins derived from silkworm cocoons that are formulated to mimic the structure of the hair's own protein matrix. The idea is not purely marketing. Silk proteins are film-forming, which means they coat the hair shaft and smooth the cuticle similarly to silicones, but they also have conditioning properties because they are structurally similar to keratin. The result is a serum that smooths and adds shine while also genuinely improving the hair's texture over repeated use.
An additional benefit is the heat-protective properties that come from the silk proteins and botanical blend. While BioSilk is not a dedicated heat protectant (see the note below in the FAQ for why this matters), it provides a meaningful buffer against heat damage up to moderate styling temperatures -- which makes it practical for anyone who blow-dries on medium heat. At $18, it delivers premium-ingredient performance at a mid-range price.
- Genuine silk protein formula with conditioning effect
- Adds real shine and smoothness
- Provides moderate heat protection
- Works on all hair types
- Mid-range price for premium ingredients
- Not a substitute for dedicated heat protectant at high temps
- Can feel slightly heavy on very fine hair
- Scent is sweet and may not suit all preferences
Bumble and bumble Hairdresser's Invisible Oil
Hairdresser's Invisible Oil earns its multi-use label honestly. The formula blends six oils -- argan, coconut, macadamia, sweet almond, safflower, and grapeseed -- each chosen for a specific property: argan for shine, coconut for penetration and moisture retention, macadamia for cuticle smoothing, sweet almond for softness, safflower for frizz control, and grapeseed for lightweight carrier. The result is a product that works whether you apply it to damp hair before air-drying, as a blow-dry primer, or as a finishing oil on styled dry hair.
The heat protection function is more meaningful here than in most oil serums -- the combination of oils creates a genuine barrier against moderate heat damage, which means you get frizz control, conditioning, and heat protection in a single step. This is genuinely useful if you want to streamline your routine. The texture is a true hybrid between a serum and an oil -- light enough not to feel heavy, but substantive enough to deliver real smoothing results.
- Genuinely works as air-dry enhancer + heat protectant + frizz serum
- Six-oil blend addresses multiple hair concerns
- Lighter feel than a single heavy oil
- Excellent for wavy and naturally textured hair
- $38 price is higher than single-use serums
- Too heavy for very fine, straight hair in larger amounts
- Not a full substitute for high-heat protectant at 400+ degrees F
Living Proof Perfect Hair Day 5-in-1 Styling Treatment
Living Proof's proprietary technology -- called OFPMA (Octafluoropentyl Methacrylate) -- works differently than silicones. Rather than coating the hair with a slick film, it creates a mesh-like structure on the hair shaft that physically blocks humidity and repels dirt and oil. This is a meaningful functional difference for thick or coarse hair types that need sustained frizz protection through the day, not just initial smoothing that fades after a few hours.
The 5-in-1 treatment also addresses strengthening, conditioning, heat protection, and softness alongside frizz control -- which makes it practical for thick or coarse hair that tends to need more conditioning support than fine hair does. Apply to damp hair before blow-drying for best results. The texture is lighter than you would expect for a treatment that does this much work, and it does not build up with daily use the way silicone-heavy serums sometimes can.
- OFPMA technology blocks humidity rather than just masking frizz
- Smooths, strengthens, conditions, protects, and controls frizz
- Does not build up with daily use
- Good value for a multi-function treatment
- Less shine than argan oil-based serums
- Less suited for fine hair that needs lightweight formulas
- Results are best when used with a blow-dryer, not air-drying alone
Not Your Mother's Smooth Moves Frizz Control Hair Serum
At $8, Not Your Mother's Smooth Moves is the easiest possible entry point into a real smoothing serum routine. The formula uses argan oil and marula oil as its primary smoothing agents -- both of which are genuinely effective at frizz control and shine at any price point. The texture is lightweight enough that it works reasonably well on most hair types without excessive heaviness. It is not going to beat the Moroccanoil in a side-by-side comparison, but the gap is far smaller than the price difference would suggest.
What makes this a recommendation rather than a budget consolation prize is availability -- it is sold in virtually every drugstore, grocery store, and Walmart, so you are not waiting on shipping when you run out. For anyone who goes through serum quickly (thick or very curly hair, or people who refresh frizz daily), the $8 price means you can actually use enough product to get the benefit without rationing. Buy it at your local store or in a multi-pack on Amazon.
- $8 price makes it easy to use generously
- Real argan + marula oil formula, not just marketing
- Available in most drugstores and grocery stores
- Lightweight enough for a range of hair types
- Less shine and lasting power than premium options
- Fragrance is noticeable and synthetic-smelling
- Not suited for very coarse or thick hair needing heavy control
OGX Ever Straight Brazilian Keratin Smooth Serum
Keratin is the protein that hair is made from, so a keratin-based serum makes structural sense for frizz control -- it temporarily fills in the raised, uneven cuticle with a compatible protein that smooths the surface and makes hair lie flat. OGX combines keratin with coconut oil, which adds conditioning and shine alongside the smoothing effect. For under $10, this formula addresses two separate mechanisms of frizz control (protein repair + oil coating) rather than just one.
The humidity resistance is a genuine standout at this price. If you live somewhere with high ambient humidity and your other serums fade by midday, the keratin in this formula tends to hold up better because it is integrated into the cuticle rather than just sitting on top of it. It is particularly effective on flyaways and the small, wispy frizz hairs that appear even on otherwise styled hair. Widely available at drugstores and Amazon. A very strong option for anyone managing frizz in humid climates.
- Keratin formula holds up in humidity better than most at this price
- Coconut oil adds conditioning + shine
- Excellent flyaway and wispy frizz control
- Under $10 at most retailers
- Coconut oil content can be too heavy for very fine hair
- Keratin is a temporary fix -- reapply after washing
- Strong tropical fragrance may not suit everyone
Quick Comparison: All 7 Hair Serums
| Product | Key Ingredient | Hair Type | Best For | Price |
|---|---|---|---|---|
| Moroccanoil Treatment | Argan Oil + Keratin | All types | Best Overall | ~$44 |
| Paul Mitchell Super Skinny Serum | Lightweight Silicones | Fine / thin hair | Best for Fine Hair | ~$25 |
| BioSilk Silk Therapy | Natural Silk Complex | Most types | Best Silk Formula | ~$18 |
| Bumble and bumble Hairdresser's Invisible Oil | 6-Oil Blend | Normal to thick | Best Multi-Use | ~$38 |
| Living Proof Perfect Hair Day 5-in-1 | OFPMA Technology | Thick / coarse | Best for Coarse Hair | ~$30 |
| Not Your Mother's Smooth Moves | Argan + Marula Oil | Most types | Best Budget | ~$8 |
| OGX Ever Straight Brazilian Keratin | Keratin + Coconut Oil | Normal to thick | Best Drugstore Keratin | ~$9 |
Related Guides
Hair serums work best as part of a broader routine. If frizz is your primary concern, pairing a smoothing serum with a good leave-in conditioner addresses both the moisture base and the surface sealing that frizz control requires. If you use heat tools regularly, a dedicated heat protectant should go on before the serum, not instead of it. And if shine and nourishment are the goal beyond just frizz control, the best hair oils on Amazon guide covers the overlap between serums and oils, including which products bridge both categories. The full hair guides index has everything organized by concern.