With the intensification of urbanization and the proliferation of high-density residential complexes, the psychological implications of living environments have become a fundamental focus in architectural and environmental psychology research. As a multidimensional construct, place attachment plays a critical role in fostering human-environment interaction, enhancing quality of life, and promoting residential sustainability. Conversely, psychological capital—representing positive internal resources—serves as a key indicator of mental health and an individual’s capacity to cope with life’s challenges. Despite the significance of these constructs, empirical investigation into the relationship between place attachment and psychological capital within residential complexes, particularly in the field of architecture, remains limited, presenting a notable research gap. The current study aims to investigate the predictive role of place attachment in determining the psychological capital of residents in residential complexes. Utilizing a quantitative, descriptive-analytical approach, this study surveyed 120 residents of two residential complexes in Tehran. Data obtained from standard and researcher-made questionnaires were analyzed using Structural Equation Modeling (SEM) via SPSS and Smart-PLS3 software. The results indicated an excellent model fit (GOF = 0.73). Regression analysis confirmed that place attachment accounts for 73.1% of the variance in psychological capital. Contrary to common assumptions, the physical dimension emerged as the strongest predictor of positive psychological resources (β = 0.641), while the social dimension ranked second (β = 0.166). Furthermore, the identity and perceptual dimensions did not demonstrate a statistically significant relationship with the optimism component (p > 0.05). These findings underscore the pivotal importance of physical and spatial qualities in fostering residents’ resilience and hope. The results highlight the necessity of re-evaluating residential design with an emphasis on sensory-evoking physical components to promote urban mental health.