This study examined the relationship between mindfulness and emotion regulation in nursing students as well as the potential mediator role of working memory capacity in this relationship. The Mindful Attention Awareness Scale (MAAS), Emotion Regulation Questionnaire (ERQ), and an Automated Operation Span Task (AOSPAN) were administered to 80 undergraduate pre-licensure baccalaureate nursing students. Pearson correlation, structural equation path modeling, and one-way ANOVA tests were conducted. MAAS scores were significantly correlated with ERQ-Reappraisal scores (r = 0.19, p = 0.045) and AOSPAN scores (r = 0.30, p = 0.004). A structural equation path model indicated that there was a direct effect of dispositional mindfulness on emotion regulation (γ11 = 0.29, p = 0.034) and working memory capacity (γ21 = 4.98, p = 0.004). However, working memory capacity did not directly mediate the effect of mindfulness on emotion regulation (b weight = −0.03, p = 0.236). Also, MAAS scores were significantly different (p < 0.05) between the student cohort levels, with the first semester students having the highest MAAS scores and the fourth semester students have the lowest MAAS scores. These findings suggest that mindfulness may influence prospective nursing professionals’ working memory capacity and ability to regulate emotions. However, working memory capacity did not explain how mindfulness influenced the use of reappraisal as an emotion regulation strategy. Nurse educators should consider other potential mechanisms of how mindfulness influences emotion regulation in nursing students. Furthermore, educators should consider that potential differences in mindfulness exist between nursing students when they implement mindfulness-based interventions.