Processes in the health sector include diagnostics, treatment, rehabilitation, prevention, education of patients, and all other interactions between qualified medical personnel and patients. Interpersonal processes pertain to the psychosocial aspect of said activities and include variables that describe communication, continuity, patient awareness, and the degree of patient involvement and influence the performance of health institutions in primary health care (PHC). The dimensions of importance for researching the influence of indicators of interpersonal processes on the performance of PHC organizations were identified, taking into account the underlying theory and specifics and characteristics of PHC. This paper studies the influence that patient-centeredness, as a dominant dimension that encompasses interpersonal processes, has on effectiveness, i.e., outcomes presented through health-related quality of life (HRQOL). Data on the factors of importance for this research subject were collected in the Republic of Serbia, while data analysis was carried out using partial least squares structural equation modeling (PLS-SEM). The research results show a complex relationship between indicators of interpersonal processes, highlight the importance of this group of processes for increasing the effectiveness of PHC organizations, and demonstrate the influence of interpersonal processes on the performance of PHC organizations.