Background : Bleaching is the most conservative treatment for discolored teeth. Direct composite veneer usually placed to improve aesthetic after bleaching. In direct composite veneer treatment, presence of free radicals residual after bleaching can inhibit the polymerization of bonding agent and decrease composite shear bond strength. This study aimed to evaluate the differences in effectiveness of 10%, 20%, and 40% guava (Psidium guajava L.) extract solution as natural antioxidant agent to improve shear bond strength of direct composite veneer to bleached enamel. Method : In this cross sectional study design, 20 extracted premolar permanent teeth were randomly colected from dental clinic and PHC around Magelang-Yogyakarta. All of the sample were selected based on exclusion and inclusion criteria. Then, the teeth were divided into four groups as follows : control group, 10%, 20%, and 40% guava extract solution group. Composite shear bond strength was measured by using Pearson Panke Equipment, Ltd Universal Testing Machine (UTM). Data were analyzed using One Way ANOVA followed by Least Significant Difference (LSD) Post Hoc test. Result : The result show that shear bond strength of control group, 10%, 20%, and 40% guava extract solution group scores were 1,33±0,42 MPa, 3,0±1,06 MPa, 2,11±0,61 MPa, and 1,94±0,65 MPa respectively. Significant highest shear bond strength values was observed in 10% guava extract solution group with significant score was 0,002 (p<0,05). There were no significant shear bond strength in control group, 20%, and 40% guava extract solution group. Conclussion : 10% guava extract solution was the most effective natural antioxidant agent to improve shear bond strength of direct composite veneer to bleached enamel with 40% hydrogen peroxide.