Objective: This study aims to investigate the impact of positive illusory bias (PIB) on the relationship between ADHD symptoms and functioning in college students, with a focus on gender differences. Method: The sample consisted of 195 college students, including 148 with ADHD and 47 without ADHD. Measures of ADHD symptomatology, life satisfaction, affect, gender identity, and impairment were collected, along with cumulative grade point average. Results: ADHD symptomatology was inversely linked to subjective well-being, with PIB acting as a significant moderator. Functional impairment was predicted by ADHD symptoms and subjective well-being, while social impairment and academic functioning were predicted by PIB and well-being. Significant gender differences were found, particularly in the interaction between PIB and ADHD symptoms for non-binary individuals. Conclusion: This study suggests that PIB is relevant for emerging adults with ADHD enrolled in higher education. Subjective well-being and PIB act as buffers against the detrimental functional and social effects of ADHD symptoms in emerging adult college students. The study highlights the importance of considering gender-specific approaches in understanding and supporting the mental health of this population.