Background <p>As individuals age, their mental health becomes critical to overall well-being. Identifying the various factors influencing psychological well-being (PWB), including social, spiritual, psychological, and individual aspects, is essential. Therefore, this study aimed to identify the factors associated with PWB among older adults visiting daycare centers in Kathmandu.</p> Methods <p>A cross-sectional path-analytical study was conducted among 300 older adults selected via a quota sampling technique (i.e., based on daycare centers). Data were collected by face-to-face interviews using seven sets of structured, valid, and reliable questions, i.e., (1) General Self-Efficacy Scale, (2) Connor and Davidson Resilience Scale, (3) Multi-Dimensional Perceived Social Support Scale, (4) Daily Spiritual Experiences Scale, (5) UCLA Loneliness Scale, (6) Lubben Social Network Scale, and (7) Psychological Wellbeing Scale, including (8) socio-demographic and comorbidity-related characteristics. Double data entry, validation, and cleaning were done using Epi-data software. Data were analyzed using SPSS version 16 software and AMOS version 21 software. Descriptive statistics, correlation analysis, and different assumption testing for the inferential statistics were employed using SPSS software. Then, the data were tested for the model fit and the path diagram using AMOS version 21 software based on 283 samples after excluding 17 multivariate influential outliers.</p> Results <p>The respondents predominantly had a moderate level (66.3%), followed by a high level (17.7%), and a low level (16.0%) of PWB. The hypothesized model of PWB demonstrated a good fit with the study data, explaining 60% of the variance in PWB through six key factors: (1) self-efficacy, (2) resilience, (3) perceived social support, (4) social connectedness, (5) spirituality, and (6) loneliness, (Adjusted <i>R²</i> = 0.60). Furthermore, the significant direct and positive effects of self-efficacy, resilience, and social support on PWB was evident. Conversely, loneliness had a significant direct and negative effect on PWB. Additionally, self-efficacy and social connectedness exhibited significant indirect and positive effects on PWB, both mediated through resilience. However, the direct effects of social connectedness and spirituality on PWB and the indirect effects of loneliness on PWB through resilience were statistically nonsignificant.</p> Conclusion <p>Resilience, self-efficacy, social support, and social connectedness are key positive factors associated with PWB among older adults, while loneliness negatively impacts it. Thus, these findings highlight the need for targeted interventions that enhance resilience, foster self-efficacy, and strengthen social support and social connectedness to reduce loneliness and improve PWB in aging populations.</p> Trial registration <p>Not applicable. The authors wish to clarify that the study design is cross-sectional, with data collected and analyzed at a single point in time. It is not a clinical trial.</p>