Abstract: ObjectiveTo examine the status of loneliness and depression among older adults in nursing homes in Huangpu District, Shanghai, and their associations with lifestyle factors, and to provide evidence for promoting mental health among institutionalized older adults. Methods From September 2023 to April 2024, a questionnaire survey was conducted among 382 older adults from eight nursing homes in Huangpu District, Shanghai, using convenience sampling. The survey collected information on demographic characteristics, lifestyle factors, loneliness, and depression. Loneliness was assessed using the 11-item De Jong-Gierveld Loneliness Scale, and depression was measured using the depression subscale of the Hospital Anxiety and Depression Scale. Spearman correlation analysis, independent-samples t tests, one-way analysis of variance, and multiple linear regression analyses were performed to examine factors associated with loneliness and depression. Results Loneliness was significantly and positively correlated with depression among older adults in nursing homes (r = 0.379, P < 0.001). Multiple linear regression analyses showed that family visit frequency (β = -0.112, P < 0.05) and sun exposure frequency (β = -0.320, P < 0.001) were significantly and negatively associated with loneliness. Weekly physical activity frequency (β = -0.281, P < 0.001), sun exposure frequency (β = -0.192, P < 0.001), and loneliness level (β = 0.253, P < 0.001) were significantly associated with depression. The loneliness and depression models explained 13.2% and 31.5% of the variance, respectively. Conclusion Loneliness and depression are prevalent among older adults in nursing homes and are closely associated with multiple lifestyle factors. Promoting regular physical activity, increasing family visits, and encouraging daily sun exposure may help improve the mental health of older adults in nursing homes.