Purpose: The objective of the analysis was to examine the relationships between sociodemographic, socioeconomic, psychosocial, and behavioural factors and both physical and mental health-related quality of life (HRQOL) in older adults. Methods: The analysis was based on recent cross-sectional data of 1687 community residents from a whole population postal survey of German adults aged 65 years and older (33% response rate, 52% female, mean age 76 years). HRQOL was assessed using the 36-Item Short Form Survey (SF-36v2). For a differentiated analysis, hierarchical multiple linear regressions were performed. Results: An internal health locus of control, physical activity, social support, and income were positively associated with physical HRQOL (Adj. R² = 0.34; p < 0.001) and mental HRQOL (Adj. R² = 0.18; p < 0.001), whereas an external health locus of control and age were negatively associated with both. Alcohol use and educational level were positively associated only with physical HRQOL, whilst female gender was negatively associated only with mental HRQOL. Conclusion: Sociodemographic, socioeconomic, psychosocial, and behavioural factors were associated with physical and mental HRQOL. These results highlight the importance of social factors in HRQOL and provide approaches for policy and practice to develop and implement tailored health interventions for older adults. Our findings may be transferable to municipalities in metropolitan areas of high-income European countries. Clinical trial registration: Not applicable.