Objectives: This study attempted to investigate the effects of castor oil on hair after preparing and applying hair-care formulations to damaged hair. Methods: With different castor oil contents (0g, 1g, 2g, 3g), hair care formulations were prepared. After applying them to hair samples, changes before and after the application were measured and comparatively analyzed. Results: L* values decreased after the application of the hair care formulations. In addition, a small increase was observed in a* and b* values. According to the measurement of de-coloring values, 20.11 NTU was found after Day 1. From Day 4, no de-coloring was observed. In terms of tensile strength, all samples using level 7 and 9 increased. According to the analysis of absorbance using methylene blue, the results slightly decreased after the application of the formulations. As for gloss, no significant difference was observed in all samples. Conclusion: When castor oil was applied to damaged hair, tensile strength increased while absorbance decreased, confirming improvements in hair texture.