We use the staggered roll-out of a mentorship program within a superstar technology firm to test whether small-scale, targeted mentoring can address organizational frictions that influence innovation and productivity. Analyzing novel data capturing the complete innovation pipeline—from initial idea disclosures through patent applications—we study seven cohorts with 633 mentees and track outcomes for over 20,000 employees. First, we find a positive, significant relation between participating in the mentorship program and innovation outcomes in the short- and long-term, with underrepresented innovators realizing the largest gains. Second, we document significant indirect spillovers through team formation, with unmentored peers experiencing productivity gains through collaboration. Survey evidence points to three mechanisms: knowledge transfer about patent processes, expanded professional networks, and increased confidence in identifying patentable ideas. The mentorship program is also associated with broader organizational improvements: engineers at the implementing firm perceive the culture to be better, report higher job satisfaction, and are less likely to leave than peers. These results suggest that small-scale mentoring programs can provide a cost-effective approach to fostering innovation and inclusivity.