Functional constipation (FC) is prevalent worldwide and is an increasingly prominent problem among university students. However, there is a paucity of research on FC in university students. This study aimed to assess the prevalence of FC among Chinese university students by the Rome III criteria and investigate its associated factors. This cross-sectional study was conducted by online questionnaires among 929 university students at a Chinese university. Food consumption was assessed with the Semi-Quantitative Food Frequency Questionnaire (SQFFQ) and dietary patterns were analyzed using factor analysis. A binary logistic regression model was applied to clarify FC-associated factors. The prevalence of FC among university students was 5.1%. Interestingly, among university students, the prevalence of FC with "complex" dietary pattern was significantly higher than those with "vegetable, fruit, egg and milk-based" and "livestock and aquatic product-based" dietary pattern (9.9% vs. 3.1% vs. 2.8%, p < 0.001). The prevalence of FC was significantly higher among university students with moderate to severe sleep disorders than those with the other sleep status (χ 2 = 18.100, p < 0.001). Furthermore, after adjusting the covariates, "complex" dietary pattern (OR = 4.023, p < 0.001), moderate to severe sleep disorders (OR = 3.003, p = 0.006), overeating (OR = 2.502, p = 0.032), long mealtime (>30 min) (OR = 6.001, p = 0.007), and poor defecation habits (OR = 3.069, p = 0.042) were positively associated with FC among university students. Based on the above-associated factors for FC, improving dietary patterns and sleep status and developing good bowel and dietary habits are essential to prevent and alleviate university students' FC.