Background: This study aimed to determine the prevalence of smoking behaviors among students in Tehran University, Iran. Methods: This was a cross-sectional study on 400 participants of Tehran University. A self-administrated, anonymous questionnaire was used for data gathering. Findings: The mean age of students was 21.70 ± 2.73 years, and 92% of them were single. The prevalence of smoking was 27.3% including 35.4% of men and 12.6% of women (P < 0.001). The mean duration of smoking was 4.22 ± 3.05 years. There was a significant association between smoking behaviors among students and their age, gender, type of accommodation, field of study, income status, duration of study, and existence of smoking habits among family members. Conclusion: The prevalence of cigarette smoking among university students is high. The lack of adequate information about smoking related diseases indicates the incapability and inefficiency of educational programs on this issue. Keywords: Smoking, University, Students, Iran.