This study evaluated the factors influencing alumni engagement with the NEMSU Graduate Tracer System by extending the DeLone and McLean Information Systems Success Model with altruism, social influence, and user attractiveness. The relevance of this work lies in combining technical system analysis, including system quality, information quality, service quality, and user satisfaction, with socio-psychological constructs that may sustain alumni participation. A quantitative design was used, and data were collected from 117 BS Computer Science graduates through a structured questionnaire. Structural Equation Modeling using WarpPLS 8.0 was applied to examine the hypothesized relationships among system-related and user-related constructs. Results show that system quality, information quality, service quality, and user satisfaction influence user intention and perceived system attractiveness. Altruism also emerged as an important engagement-related construct, indicating that alumni participation is supported not only by technical functionality but also by the perceived value of contributing to the institution. Social influence showed a positive but comparatively weak significant effect on user intention with beta = 0.12 and p < 0.01, suggesting that peer or institutional encouragement may contribute to participation but is less influential than system functionality, satisfaction, and personal value. The study is limited by its sample size and focus on one department; therefore, broader validation with larger and more diverse alumni groups is recommended. The findings suggest that sustainable Graduate Tracer Systems should balance technical reliability, usable design, emotional appeal, and prosocial motivation to strengthen long-term alumni engagement.