We investigated the effects of mentoring on selected attributes among high-school mentors. Three attributes were explored: altruism, diligence, and student leadership. Sixty-eight high-school juniors and seniors participated as mentors to high-school freshman students. Mentors participated in a leadership training program prior to beginning their mentoring activities. Pre- and post-test measures of the three attributes were administered using a paired t-test. Results showed no significant increase in diligence scores, and a significant increase in the perception of leadership scores. Unexpectedly, the mentoring experience produced a significant decrease in altruism scores throughout the 2015-2016 school-year. Implications for implementing a mentoring program in a high school setting are discussed.