The current study tested whether relationships with natural mentors may have contributed to fewer internalizing symptoms and less substance use among emerging adults through improved perceptions of coping abilities and an increased sense of life purpose. In addition, the current study investigated whether natural mentor role (i.e., familial vs. nonfamilial mentor) and the amount of time spent together in shared activities influenced emerging adults' internalizing behaviors and substance use via coping and purpose. Participants in the current study included 3,334 emerging adults (mean age = 20.8, 48.6% female, 75.4% white) from diverse regions across the United States who participated in an online survey. Participants were recruited via an adapted Web version of Respondent-Driven Sampling (webRDS). Forty-two percent of participants reported a relationship with a natural mentor. Indirect relationships between natural mentor presence and emerging adults' mental health and substance use via coping and purpose were found. Additional analyses indicated that emerging adults may benefit more from relationships with nonfamilial natural mentors in comparison with familial natural mentors. Findings also suggested that the amount of time participants spent with their natural mentors in shared activities was related to participants' alcohol use. Implications of this study's findings and directions for future research are discussed.