Higher education has changed as the prevalence of online education has increased. More adults with full time jobs are returning for a graduate education and many of them choose the online modality due to their responsibilities, priorities, and sources of support. Therefore, we need to analyze factors that make online graduate students successful in their educational journey. Using a time-lagged sample of 244 online graduate students this study employed SEM to examine the role of intrinsic motivation, engagement, and work-school-family inter-role conflict in the success of online graduate students. Results show students' intrinsic motivation has a positive impact on student success measured by self-reported learning (β = 0.33, ρ < 0.01, R2 = 0.12) and grade (β = 0.21, ρ < 0.01, R2 = 0.05). Engagement partially mediates the relationship, greatly increasing the explanatory power of the model (learning R2 = 0.34, grade R2 = 0.09). Work-school-family inter-role conflict moderates this relationship, significantly weakening the positive relationship between intrinsic motivation and engagement (β = −.14, ρ < 0.01). These findings increase our understanding of elements impacting students’ success. Recommendations on how to maximize the positive impact of intrinsic motivation on engagement and reduce the negative impact of inter-role conflict, as well as suggestions for future research in the area, are provided.