Intergenerational theater activities have been recently employed in recreation for older adults. We held a series of four intergenerational theater workshops in two older adults’ care facilities in Japan and sought the experiences of older participants, younger participants, and the facility managers. With a qualitatively driven mixed-methods multiple-case study design, we obtained data from field observation, interviews with participants, and preworkshop and postworkshop changes on a well-being scale (Ikigai-9) among older participants, and the results of the two sites were compared. “Immediate effects” were seen in older adults because they responded actively and demonstrated surprising faculties during the workshop. Facility staff members and younger participants received “extended effects” because they gained new ideas regarding the remaining skills of older participants and a sense of reuniting with old neighbors through the exercise. In the Ikigai-9 scale, the items measuring “present happiness” significantly improved at Site 1 but not at Site 2. Better results at Site 1 might have been caused by the lower care needs of participants and the inclusion of children. Less support from facility staff members during the activities also might have promoted the voluntary participation of older adults. Involving children and engaging the facility staff in preparation could enhance the quality of activities.