Social dominance and prosocial behavior has widely been studied by researchers in developed countries, yet there exist a wide knowledge gap needed to be filled on these variables in Nigeria especially among students of tertiary institutions. Hence, this study investigated the effects of perceived similarity and self-concept on social dominance and prosocial behavior among some undergraduates Using cross-sectional survey design with a purposive and accidental sampling technique, a total sample of 238 undergraduates consisting of 118 males (49.6%) and 120 females (50.4%) respondents with their ages ranging from 16 to 40 (M =1.95; SD=.78). Two hypotheses were formulated and tested with 2X2 ANOVA. The result confirmed a significant effect of self-concept on social dominance [F(1, 234) =9.30, P .01], however, no significant effect was found for perceived similarity on social dominance [F (1, 234) =.205, P .05]. Also, perceived similarity and self-concept did not have an interaction effect on social dominance [F(1, 234) =.08, P .05]. In addition, perceived similarity [F(1, 234) =15.01, P .01] and self-concept [F(1, 234) =534.53, P .01] had significant main effects on prosocial behaviour. Also, there was an interaction effect of similarity and self-concept on prosocial behaviour [F (1, 234) =5.36, P .01]. The study therefore recommends that prosocial education should be embraced and taught in tertiary institutions as one of the courses. This will help students to form a positive attitude towards others thereby breeds oneness, progress and wellness in the society.