Rivers2Lake helps teachers learn to provide watershed educational experiences for students through a summer institute followed by mentoring. Teacher focus groups were conducted to investigate the impact of mentoring, as well as toward understanding what was influential in bringing about those impacts. Mentoring impacted teachers in affective ways and helped them use what they learned at the institute. The influential nature of the mentoring may be due to the mentors providing a sense of accountability, personalized support, as well as encouragement of reflection and assistance with navigating barriers. Teachers also articulated qualities of effective mentors: invested, flexible, and responsive. With teachers varying in the degree to which they felt they could continue R2L implementation without the support of mentors, implications are discussed.