Purpose: The study aimed to investigate the effects of tea tree oil on damaged hair.Methods: A texture-improving agent was produced by adding different dosages of tea tree oil (i.e., 0, 2, 4, and 6 g) on sample hair. Comparative analysis was conducted by measuring the effects of the agent before and after application to sample hair bleached into level 8. To examine changes in hair brightness, L* value was measured using a color difference meter. In addition, to determine the effects of the agent on damaged hair, the study measured tensile strength, absorbance using methylene blue, and hair gloss.Results: The mean L* value for each sample increased for healthy hair but decreased in the 8L samples. Analysis indicates that the healthy hair, 8L(4) sample, and 8L(6) samples pointed to significant results. The mean value for tensile strength increased for all healthy and 8L hair samples after application. Specifically, the 8L(4) and 8L(6) samples displayed significant results. In terms of absorbance, the mean value decreased for all healthy and 8L hair samples after application. Moreover, hair gloss values increased for samples applied with the agent containing tea tree oil. Specifically, the 8L(2), 8L(4), and 8L(6) samples exhibited increased values after application.Conclusions: The results confirm the effects of tea tree oil on damaged hair in terms of improvements in terms of tensile strength, absorbance, and gloss. The study recommends that further research on the effects of various oils and natural extracts on damaged hair is necessary in terms of improving other hair characteristics and using more samples.