Although volunteering has been associated with numerous social benefits for diverse older adults, there is little information on how they establish relationships within a multicultural volunteering program outside of their co-ethnic communities. This convergent mixed-method social network study adopts the bonding and bridging social capital theory to explore the structures and dynamics of social interactions within a multicultural volunteer program. Low-income Russian, Khmer, Somali, Nepali, and English-speaking older volunteers in the Senior Companions Program (SCP) in a Midwest metropolitan ( N = 83) participated in the surveys and focus groups. Homophily coefficients ( r) show that the SCP volunteers mostly interacted with people who identified with the same nationality ( r = .86), race ( r = .87), and gender ( r = .50). Qualitative results suggested that volunteers strengthened their social networks through within-cultural social bonding while appreciating opportunities for cross-cultural social bridging. Compared with within-cultural social bonding, cross-cultural social bridging in multicultural volunteer programs require intentional facilitation, resources, and organizational commitment.