The growing aging population presents unique challenges in maintaining their quality of life (QoL), which encompasses physical, psychological, and social wellbeing. This study aimed to assess the impact of multidisciplinary collaboration on QoL among older patients receiving primary care. A cross-sectional study was conducted involving a purposive sampling of 200 participants aged 60 years and above from Primary Healthcare Centers in Al-Ahsa, Saudi Arabia, between March and May 2024. Data were collected using standardized tools: SF-36 for health-related QoL, Multidisciplinary Collaboration Evaluation Tool (MCET), and Lubben Social Network Scale (LSNS). Multivariate regression analyses were performed to examine the associations between multidisciplinary collaboration, social support, and QoL outcomes. Multidisciplinary collaboration exhibited a significant positive association with improvements in physical functioning (β = 2.35, p < 0.001), mental health (β = 3.01, p < 0.001), and general health perceptions (β = 2.12, p < 0.001). Key drivers of effective collaboration included effective communication (β = 0.48, p < 0.001), coordination (β = 0.42, p < 0.001), and patient involvement (β = 0.40, p < 0.001). Social support, particularly from friends (β = 0.33, p < 0.001) and family (β = 0.28, p < 0.001), was also a robust predictor of better QoL. Younger age, female gender, married status, and absence of chronic conditions were associated with greater QoL improvements from multidisciplinary care. Multidisciplinary collaboration and social support networks significantly enhance QoL among older primary care patients. Healthcare systems should prioritize developing collaborative care models, fostering interdisciplinary teamwork, and integrating strategies to promote social connectedness for the aging population.