This study aims to investigate the quality of life (QOL) of Tehran University of Medical Sciences' (TUMS) medical students at different educational levels and specify the most important factors related to this quality. A sample of 242 medical students was selected randomly, given their number in three educational levels (basic sciences, physiopathology-stager and intern). The QOL was measured by WHOQOL-BREF. The students obtained average high score in two psychological and environmental health domains, and low score in physical health and social relationship domains. As the educational level of students increased their quality of life decreased at all four domains. At social relationship domain, the female students had overall better situation as compared to males (p=0.009). The female and male students had opposite condition at the level of basic sciences and internship, in a way that the female students earned higher marks at basic sciences level and the males at internship level (P= 0.008). The condition of female students in terms of environmental, physical and psychological health became static while their education rose. However, only environmental health of the male students reduced as their education level increased (P= 0.05). The students were of undesirable conditions in two domains of social relationship and physical health. Internship is a specific level in both groups which has a negative impact on the dimensions of quality of life and naturally needs more care for the students. Married status improved the students' QOL and could moderate the undesired effects of internship.