Background: Physical activity is a very positive behavior that has many health benefits, so understanding current physical activity levels in specific populations is important for health policy planning. Objective(s): to estimate physical activity patterns and to investigate the relationship between physical activity performance and using smartphone health applications among university students in Riyadh, Saudi Arabia. Methods: This cross-sectional study estimated physical activity patterns among King Saud University students. An online survey was distributed to all students attending King Saud University. The survey included questions on socio-demographic characteristics and the International Physical Activity Questionnaire Short Form (IPAQ-SF). Results: A total of 427 students were enrolled in the study. More than half of the students were low in physical activity (56.2%) followed by moderate and high levels (30.7 %, and 13.1% respectively). More than half of them used their smartphones five hours or more per day (53.6%), and the majority (65.1%) used applications to monitor physical activity. Bivariable analysis revealed a significant association between physical activity and using applications to monitor health and using applications or wearable devices to monitor physical activity. Additionally, a significant association between physical inactivity and hours of using a smartphone per day was detected. Conclusion: Low physical activity was prevalent among students at King Saud University. Targeted interventions are needed to enhance physical activity and prevent sedentary behaviors to prevent long-term adverse health consequences.