Gender is among the determinant factors affecting students' academic achievement. This paper tried to investigate the impact of gender on academic performance of preparatory secondary school students based on 2014 EHEECE result. Ex post facto research design was used. To that end, data were collected from 3243 students from eight purposively selected schools. The analysis has been undertaken quantitatively using independent samples t-test, one sample t-test, Pearson correlation coefficient, Chi-square test, ANOVA and linear multiple regression. The findings revealed that there is statistically significant difference between male and female students favoring the former. Sample mean is statistically higher than regional and zonal mean scores. A statistically significant difference among sampled schools has been observed. Younger students have scored significantly higher result than the older ones. The proportion of male students in the upper achieving groups was significantly higher than females and the opposite was true for low achieving groups. More effort is needed by concerned bodies so as to narrow the gender disparity. Furthermore, additional studies should be conducted to investigate the performance differences among schools.