The objectives of this study were to investigate the relationship between adolescent self-efficacy, self-esteem, aggression, gender and their academic performance. The data were gathered through three Likert type scales (self-efficacy,rnself-esteem, and aggression) and data on their academic performance, were collected from the record offices of their respected schools. A total of 286 (225 male and 61 females) high school adolescent students ranging from 15 to 18 years of age attending grade nine and ten in the Gambella Region constitute the sample. The sample was selected through proportional stratified random sampling method. The results were analyzed using mean, standard deviation, Pearson correlation, t-test and multiple regression. The Intercorelation matrix result indicated that self-efficacy and academic achievement had a positive correlation of r=0.15, p < 0.05; and aggression and academic achievement had a negative correlation 0/1'=-0.18, p < 0.01 ; and aggression and self-esteem had a negative correlation of r=-0.22, p < 0.01. The contribution of gender, aggression. self-efficacy together accounted for 10.40 percent of variation in academicrnachievement. Gender was positively and significantly related to academic achievement (r=0.20, p < 0.05) . A statistically significant difference was obtained in academic achievement and aggression in /c/1'or of males t (284/) =3.4343, P 0.05. It indicates that students' genderrndifference influences their academic achievement. Hence, due attention should be given in enhancing self-efficacy and self-esteem and minimizing aggression of adolescent students in order to facilitate a better academic performance inrnschools.