Objective: The purpose of this study was to understand the lived experiences of supplementary grandparents with their grandchildren during co-occupations. Methods: The researchers enrolled eight grandmothers and one grandfather, with grandchildren ages six months to 21 years. Using a phenomenological design, the researchers gathered data through surveys, individual semi-structured interviews, and a focus group interview. Researchers completed individual and collective coding to identify themes. Results: Participants varied in age, employment status, marital status, and proximity to their grandchildren, extending from 10 minutes to more than two hours. Findings revealed that participation in co-occupations between grandparents and grandchildren enhanced their relationship and encouraged an active lifestyle of grandparents. Grandparents also experienced physical and cognitive demands during co-occupations, prompting modifications to preserve participation. Grandparents described the purpose of co-occupations as having fun, teaching, and learning from grandchildren. The results indicated that co-occupations were influenced by grandparents’ employment status, the age of the grandchildren, the health of the grandparent, the relationships between parents and grandparents, and the proximity to grandchildren. As grandchildren aged, the grandparents’ roles in co-occupations shifted from active participants to observers and supporters. Conclusion: The findings of this study can help occupational therapy practitioners understand the benefits and challenges associated with co-occupations of grandparents and grandchildren.