The interplay between mindfulness, stress, and academic major satisfaction remains unexplored in the Nigerian population. This study aimed to investigate these factors among Nigerian undergraduates, exploring the moderating roles of gender and age. A cross-sectional design was employed with 184 undergraduates. Data were collected online using the Mindful Attention Awareness Scale (MAAS), the Academic Major Satisfaction Scale (AMSS), and the Academic Stress Scale (ASS). Pearson correlations and moderation regression analyses were performed. Participants reported moderate mindfulness and academic stress, but low major satisfaction. MAAS negatively correlated with ASS (r = -0.428, p < .001) and with AMSS (r = -0.224, p = .002). AMSS positively correlated with ASS (r = 0.384, p < .001). Gender significantly moderated the MAAS-AMSS relationship (β= 0.072, p = 0.014), with a stronger negative association for males. Age moderated the ASS-AMSS relationship (β=−0.096, p=0.012) and the combined MAAS-ASS-AMSS relationship (β=0.011, p=0.038), weakening the stress-satisfaction link for older students. Mindfulness reduces academic stress, but its relationship with major satisfaction is complex and can be negative. The positive link between stress and satisfaction may reflect deep investment. Gender and age are significant moderators, highlighting the need for tailored interventions for student well-being in Nigerian universities.