Objective This study aimed to understand the knowledge, attitudes and practices (KAP) on seasonal influenza among medical college students in a low-income multiethnic society. Methods A cross-sectional questionnaire survey collected information of KAP related to influenza. A knowledge score was calculated according to the total number of correct points out of 9 questions. Logistic regression was used to identify factors associated with influenza vaccine uptake. Results 856 valid questionnaires were obtained. The average knowledge score was 14.8 ± 3.1 out of 22 correct points. Han Chinese got higher score than minorities (p < 0.001). Knowledge score increased with grade (p < 0.001). Students majoring in pharmacy had lower score than others. Questions on mode of transmission, symptoms, precautions, high risk groups and vaccination schedule had a correct rate lower than 50%. Hand hygiene was practiced by less than 40% of students after touching objects in public areas or sneezing. The proportion of participants received influenza vaccine in the past 3 y was 4.1%, 9.2% and 6.1% respectively. Willingness to receive free vaccine (OR = 2.49, 95% CI 1.31∼4.28), and awareness of the vaccine effectiveness (OR = 1.67, 95% CI 1.08∼2.56) were significantly associated with vaccine uptake, while the general knowledge about influenza, perceived susceptibility and severity, and demographic factors were not. The top 3 reasons for not being vaccinated were poor knowledge of the vaccine (46%), no perceived need due to good health (45%) and worry about adverse reactions (33%). Conclusion Health education is needed to improve the awareness of basic facts about influenza and vaccine, and more attention should be paid to minority groups. The coverage of seasonal influenza vaccine is quite low. Besides individual level behavior change, social and structural factors should be considered to increase the uptake of influenza vaccine.