Addressing the psychosocial needs of vulnerable children and youth is viewed increasingly as a priority of humanitarian programs, particularly in Africa, where the scale of the problem necessitates community-based solutions. This quasi-experimental study tested a model of adult mentorship and support to improve psychosocial outcomes among youth-headed households in a rural area of Rwanda. Two rounds of data were collected from youth who served as heads of their households. Following the baseline survey in 2004 (n = 692), an adult mentorship program was implemented among half the sample. A follow-up survey was conducted after 18 months of intervention exposure (n = 593). Through regular home visits, mentors developed a stable, caring relationship with youth in their community living without an adult caregiver. Each mentor was assigned 2–3 youth-headed households located within their own community to visit at least once a month for 2–3 hours in the home. Over an 18-month period, 156 trained adult mentors (60% male, 40% female) visited and supported 441 households. Multivariable analyses explored linkages between exposure to the intervention and four key psychosocial outcomes: perceptions of adult support, marginalization, grief and symptoms of depression. Over time, youth with a mentor reported a significant increase in perceptions of available adult support and decreases in marginalization. While grief in the comparison group grew significantly over time, grief levels in the intervention group remained stable, suggesting that the mentorship program may have mitigated grief among youth in the intervention areas. Intervention respondents also reported a slight, but significant, decrease in depressive symptoms. Findings suggest that the mentoring program enhanced available support and community connectedness among youth in this study. However, program impact on emotional wellbeing was more modest. More intensive interventions may be needed to reduce grief symptoms and for those with high levels of depressive symptoms.