The study examined the role of self-regulation; as a mediating variable, in the relationship between grit and academic achievement. The sample included 211 students from Sultan Qaboos University. The study used a descriptive approach. To achieve the objectives of the study, two scales used: self-regulation (Pintrich et al., 1991), and grit (Alhadabi et al., 2019). The results of Baron & Kenny (1986) multiple regression analysis showed a statistically significant effects of grit in self-regulation and academic achievement, and statistically significant direct effects of self regulation on academic achievement. Moreover, the results showed that the self-regulation mediated the relationship between grit and academic achievement. The findings also showed a high level of self-organization, an average level of grit, a good level of academic performance among Sultan Qaboos University students, and a positive statistically significant correlation between grit, self-regulation and academic achievement. The findings also highlighted differences in level of both self-regulation and grit attributable to the gender variable in favor of females, while there are no statistically significant differences of academic achievement, and there are no statistically significant differences between students of scientific colleges and humanities colleges in the level of self-regulation, grit, and academic achievement.