Background and Study Aim. The relationship between coach and athlete may significantly influence an athlete's experience in sports. Elements such as closeness, commitment, and complementarity are key aspects of this relationship. The current study aimed to examine the association between motivation and athletes' engagement in sports, as mediated by the coach-athlete relationship. Material and Methods. A sample of 408 student-athletes from various universities in Iligan City participated in the study. They completed a set of questionnaires assessing motivation, the coach-athlete relationship, and athlete engagement. The participants were between 18 and 25 years old. The measures used in the study included the Coach-Athlete Relationship Questionnaire (CARTQ), the Sports Motivation Scale (SMS), and the Athletic Engagement Questionnaire (AEQ). Ethical approval was obtained from all participants. Results. The results showed that coach-athlete relationships were characterized by closeness, commitment, and complementarity. These relationships significantly mediated the link between intrinsic and extrinsic motivation and athlete engagement in sports. Strong connections between coaches and athletes enhance the positive effect of motivation on engagement. This occurs by fulfilling athletes' psychological needs for autonomy, competence, and relatedness. Conversely, amotivation was negatively associated with engagement through the dimensions of the coach-athlete relationship. Athletes with high levels of amotivation are more likely to disengage. This highlights the need for coaches to foster a supportive environment that reduces negative motivational states. Conclusions. The evidence supports the utilization of Self-Determination Theory (SDT) to better understand the importance of relationship factors in enhancing motivation. This approach leads to long-term engagement in sports. These results offer a more comprehensive view of the delicate dynamics of the coach-athlete relationship and its consequences for motivation and athletic engagement in sports.