Academic achievement is regarded among the important achievements of every educational system that the mental health of students can have important role in realizing these goals. So, this research has been performed aiming at investigation of the relationship between mental health and academic achievement of dental students of Ahvaz Jundishapur University of Medical Sciences (AJUMS).In the descriptive-analytical study, 120 dental students(professional doctorate) were selected as research sample by simple random method in 2016. The data collection tool was GHQ-28 questionnaire. The students’ Grade Point Averages (GPA) of previous semester have been considered as their academic achievement indicator. Data analysis was performed by using descriptive statistics (frequency, mean, and standard deviation) and inferential statistics (t-test, analysis of variance, and correlation test). The results of research indicated that there is a significant difference between the mental health of married and single (P<0.05) and female and male (P<0.05) students under study. No significant relationship was observed between mental health dimensions and academic success either (P>0.05), although there was significant and reverse relationship between the students’ mean scores of mental health questionnaire and academic achievement (R=0.293). It means that by mental health enhancement (the low total score in test) the students’ GPA (as academic achievement indicator) increase. Thus, with regard to the point that providing students’ mental health has important role in their academic achievement and also all-round development of every country, it is essential to consider special measures to provide it for the students appropriately.