<p>This study aimed to investigate the bidirectional longitudinal relationship between sports and exercise and phubbing behavior among university students, with particular emphasis on their dynamic individuals with high initial levelss and developmental trajectories, thereby providing evidence-based interventions for promoting healthier lifestyle behaviors in this population. Using a cluster sampling approach, 689 college students (mean age = 20.34 years) were recruited from four universities in China and surveyed at three time points over one year, with 585 valid questionnaires retained for analysis. The “Physical Activity Rating Scale (PARS-3)” and the “General Scale for Phubbing Behavior (GSPB)” were employed to measure the variables. Cross-lagged regression models and parallel latent growth modeling (PLGM) were applied. Both sports and exercise and phubbing behavior exhibited significant longitudinal stability. Phubbing behavior negatively predicted subsequent levels of sports and exercise (<i>β</i> = -0.28), with this effect being stronger than the reverse prediction (<i>β</i> = -0.24). (2) Higher initial levels of phubbing behavior not only negatively predicted subsequent sports and exercise levels but also negatively predicted the rate of increase in sports and exercise over time (<i>β</i> = -0.35). (3) Conversely, higher initial levels of sports and exercise were significantly associated with lower levels of phubbing behavior. Sports and exercise may serve as a protective factor against the development of phubbing behavior, while excessive phubbing behavior significantly inhibits engagement in sports and exercise. Targeted interventions—such as promoting sports and exercise programs, psychological counseling, and peer-based reminder systems—are recommended to mitigate the adverse effects of phubbing behavior and foster healthier lifestyles among college students.</p>