Olaplex Nº. 9 Bond Protector Nourishing Hair Serum

Olaplex Nº. 9 Bond Protector is the brand's answer to the question: what if a heat protectant also repaired your hair? The formula combines Olaplex's patented bond-building technology with a nourishing serum base that softens, detangles, and reduces static — all while providing meaningful protection against heat styling and environmental stressors.

We tested this on color-treated, fine hair that is prone to heat damage from daily blow-drying and flat-ironing. Applied to damp hair before styling, it distributed evenly without weighing strands down. The result was noticeably smoother, shinier hair with significantly reduced frizz. Unlike silicone-heavy heat protectants that simply coat the hair shaft, No. 9 works cumulatively — with regular use, hair becomes progressively stronger and more resilient.

At current pricing for 3 oz, it's a premium price for a heat protectant, but the dual functionality — protection plus bond repair — justifies the cost for anyone already invested in the Olaplex system. For those who heat-style daily and want their protectant to do more than just protect, No. 9 is the most advanced option available.