Background <p>Adherence to immunosuppressive therapy in organ transplant patients is an important factor for the patient’s health and the success of the transplant. In this study, we investigated the relationship between the perceived level of social support and adherence to immunosuppressive therapy in post-transplant patients.</p> Methods <p>This descriptive and cross-sectional study was conducted with 116 post-transplant liver and kidney transplant recipients. Data were collected using the Personal Information Form, the Multidimensional Perceived Social Support Scale, and the İmmunosuppressive Therapy Adherence Scale (ITAS). Statistical analyses were performed using IBM SPSS Statistics version 30.0, and the significance level was set at <i>p</i> &lt; 0.05.</p> Results <p>The mean age of the participants was 41.52 ± 12.23&#xa0;years. Of the patients, 62.7% had undergone kidney transplantation and 37.3% had undergone liver transplantation, with the majority (83.9%) receiving organs from living donors. The overall adherence to immunosuppressive therapy was relatively high, with 51.7% of the patients achieving full adherence (ITAS = 12), with a mean ITAS score of 10.22 ± 1.30 (out of 12). A positive and significant relationship was found between adherence to immunosuppressive therapy and perceived level of social support (<i>B</i> = 0.052, <i>p</i> &lt; 0.001).</p> Conclusions <p>The importance of social support in the post-transplant period should not be overlooked; in particular, the involvement of family, friends, and other significant individuals should be systematically integrated into patient care. In this context, perceived social support is a practical and feasible strategy for improving adherence to immunosuppressive therapy. Healthcare professionals should routinely assess patients’ levels of social support and implement targeted psychosocial interventions for individuals with inadequate support.</p>