Background <p>Clown visits are increasingly used as psychosocial interventions in long-term care settings. However, existing evidence is predominantly qualitative and/or short-term, with a lack of controlled longitudinal studies examining effects across affective, resilience-related, sleep-related, and functional outcomes. Moreover, the role of individual-based visit frequency remains largely unexplored.</p> Methods <p>This longitudinal controlled field study examined the effects of clown visits over two years in four long-term care facilities in Eastern Germany. The intervention group comprised <i>n</i>_{<i>IG_T0</i>} = 135 residents at baseline, <i>n</i>_{<i>IG_T1</i>}= 163 after one year, and <i>n</i>_{<i>IG_T2</i>}= 121 after two years; the control group included <i>n</i>_{<i>CG_T0</i>}= 27, <i>n</i>_{<i>CG_T1</i>}= 50, and <i>n</i>_{<i>CG_T2</i>}= 43 participants. An additional waiting control group included <i>n</i>_{<i>WGC_T−1</i>}= 43 residents assessed prior to intervention onset. Validated self- and proxy-report measures assessed affect, resilience, sleep quality, and functionality. Multilevel models were used to analyse group differences in change over time and to test individual-based visit frequency as a moderator; exploratory multilevel analyses distinguished within-person and between-person associations.</p> Results <p>After one year, residents receiving clown visits showed more favourable developments in sleep-related outcomes and depressive mood than the control group. After two years, the declines in positive mood and resilience were significantly less pronounced in the intervention group. No consistent effects emerged for other functional domains, and visit frequency did not moderate longitudinal change. Exploratory analyses indicated that, within individuals, higher visit frequency was associated with greater self-care difficulties, disorientation, withdrawal, lower resilience, and higher daytime sleepiness; between individuals, it was linked to higher disorientation, positive affect, and lower negative affect.</p> Conclusion <p>Clown visits showed time-specific benefits for residents’ mood, sleep quality, and resilience - without adverse effects. Their contribution appears to lie particularly in supporting residents’ emotional well-being and sustaining resilience over time, rather than broadly altering functional trajectories. The pattern of visit frequency underscores an adaptive delivery aligned with residents’ psychosocial and functional needs, highlighting clown visits as a flexible, context-sensitive intervention embedded in everyday care. As such, clown visits may contribute to preventive care and supportive emotional climate in long-term care, with potential benefits for nursing practice.</p> Trial registration <p>Not applicable.</p>