Students' ability to learn effectively and perform well in their academic curriculum largely depends on their motivation level to achieve. Drawing upon Achievement goal theory (AGT) and Self-determination theory, this study investigated how students' goal orientation, especially mastery-goal and performance-goal, influences academic outcomes and agentic engagement via intrinsic motivation as a mediating mechanism in a unified structured model. While previous studies have identified the separate associations between goal orientation and academic learning outcomes and engagement, there was a lack of studies to explore the dynamic and interactive effect of goal orientation leading to different academic outcomes. Mastery goal orientation was constantly connected to adaptive and beneficial outcomes, whereas the effect of performance-goal orientation is context-based ambiguity, which inspired this study to clarify the consequences brought by performance-goal orientation. The study utilized quantitative method using Structural Equation Modeling (SEM) method and full mediation model for data analysis. The study collects data from 141 Chinese university students as the main respondents. The results underscore that mastery-goal orientation, as a stronger predictor compared to performance-goal orientation, is significantly related to higher intrinsic motivation, which in turn predicts improved agentic engagement and reduced academic burnout. Though the path from performance-goal to intrinsic motivation was not significant, it demonstrates a positive trend. This full mediation model discloses intrinsic motivation as a key mediator between the studied variables. This study has theoretical and practical implications, which display a unified model about the effect of goal orientation on students' academic outcomes and effort input, contributes an empirical perspective to educators' classroom practice, and provides a comprehensive understanding of higher education.