Gamification is a modern concept that makes physical and digital activities engaging and enjoyable just like games. Game elements are added to mobile applications for user retention and engagement. One of the dark sides of gamification i.e., addiction is explored in this novel study in the context of mobile application design. It uses a mixed-method approach to lay the foundation of the relation between gamification and Smartphone Addiction, which is critically explained in a limited literature review using existing theories and studies on gamification. Interviews with behavioral experts confirm the psychological aspects of the research. The study also identifies game elements that contribute to smartphone addiction by a survey analysis of 269 participants. Results reveal Scrolling and Tapping as most addictive game elements. Some elements also show a statistically significant relationship with daily smartphone usage in hours. There are many effective applications of gamification, and in the context of mobile application design, it indeed helps to increase user engagement, however, there is an ethical need to reflect on what the exaggerated form of this engagement can lead to. As future research, a longitudinal study and experiments are suggested to find out this relationship with the use of empirical data.