Objectives: Physical activity in people with dementia (PwD) may enhance physical and mental functioning. Exergaming, which combines physical exercise with cognitive stimulation in a gaming environment, was developed to overcome barriers in performing physical activities. We evaluated the effects of exergaming in day care centers (DCCs) for PwD and informal caregivers (ICs). Design: A randomized controlled trial among 23 DCCs across the Netherlands randomized to exergaming (interactive cycling during 6 months) or a care-as-usual control group. Setting and Participants: A total of 112 (73 exergaming, 39 control) community-dwelling dyads (PwD, IC), with the PwD visiting a DCC at least twice per week. Methods: All outcomes were assessed using structured questionnaires during interviews with PwD and ICs at baseline (T0), 3 months (T1), and 6 months (T2). Primary outcomes: physical activity and mobility of the PwD. Secondary outcomes: physical, cognitive, emotional and social functioning, and quality of life for PwD. For ICs: experienced burden, quality of life, and positive care experiences. Results: Mixed-model analyses showed no statistically significant effects on primary outcomes. There were statistically significant positive effects on PwD's secondary outcomes at T2 on cognition [Mini-Mental State Examination (MMSE): r = 2.30, 95% confidence interval (CI): 0.65, 3.96, P = .007; and Trail Making Test part A (TMT-A): r = −28.98, 95% CI: −54.89, −3.08, P = .029], social functioning (Behavior Observation Scale for Intramural Psychogeriatrics subscale 1 (GIP): r = −1.86, 95% CI: −3.56, −0.17, P = .031), and positive post-test effects in ICs on distress caused by the PwD's neuropsychiatric symptoms (NPI-Q total distress: r = −3.30, 95% CI: −6.57, −0.03, P = .048) and on sense of competence (SSCQ: r = 2.78, 95% CI: 0.85, 4.71, P = .005). Conclusions and Implications: Exergaming appeared not effective on the primary outcomes. Despite the study being underpowered, we found positive effects on secondary outcomes for PwD and ICs, and no negative effects. We therefore recommend further study, dissemination, and implementation. © 2020 AMDA – The Society for Post-Acute and Long-Term Care Medicine