Objective:To investigate smartphone addiction among medical students and to determine factors associated with smartphone addiction among sixth-year medical students at King Abdulaziz University, Jeddah.Methods:This cross-sectional study was conducted on 203 sixth-year medical students at the Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia, during July 2017. Data analysis was done using SPSS-20.Results:The number of completed questionnaires received was181 out of 203, making a response rate of 89%. There were 87 male respondents (48.1%) and 94 female respondents (51.9%). The overall prevalence of smartphone addiction was 66 (36.5%). There is a statistically significant relationship between daily hours of smartphone usage and smartphone addiction (p<0.02). Out of 66 addicted students, 24 (55.8%) students reported using their smartphone more than five hours daily, 17(34.7%) students were using it 4 to 5 hours daily, 13 (27.7%) students were using it 2 to 3 hours daily and 12(28.6%) students were using it less than two hours daily. The study showed no statistically significant relationship between smartphone addiction and smoking statusor degree of obesity. There was a significant association between the total score on the smartphone addiction scale and daily usage hours (p-value<0.005).Conclusion:The overall prevalence of smartphone addiction was high among our study participants. The smartphone addiction was associated with daily hours of smartphone usage.