Background: The relationship between patients and healthcare professionals (physicians) is the cornerstone of successful long-term antiretroviral therapy for people living with human immunodeficiency virus (HIV). Purpose: This study aimed to investigate the connection between involvement, perception, and understanding as the basis for the patient–physician relationship and drug adherence, measured as the probability of non-adherence. Methods: In an online survey, people with HIV were asked about their relationship with their physicians and the extent to which they felt involved in treatment-related decisions. A statistical analysis was conducted to determine whether a better patient–physician relationship was associated with higher adherence to therapy. This was performed by univariate group comparison (Mann–Whitney-U, Fishers Exact Test) and logistic regression. Results: A total of 303 persons living with HIV participated in the survey, and 257 patients were included in the analysis. Overall, 27.6% were classified as non-adherent and self-reporting based on whether an antiretroviral therapy (ART) was taken in the past or how often the ART was interrupted. This proportion was significantly higher among patients aged 50–74 years (39.7%) and those with a longer therapy duration (9–15 years: 46.6%; from 15 years on: 55.8%). Therapy-non-adherent patients showed significantly lower scores in the relationship aspects understanding (2.68 vs. 3.03), participation (2.63 vs. 3.07), and perception (3.00 vs. 3.24) compared to adherent patients. Logistic regression analysis confirms that higher scores for understanding, involvement, and perception are strongly associated with a reduction in the risk of becoming non-adherent. This was true for all examined regression models, regardless of whether they were adjusted for the length of therapy and socio-demographic characteristics. Conclusion: The results reinforce the need for awareness among health care professionals (HCP) regarding understanding, involvement, and perception as important aspects to improve the quality of the patient–physician relationship for high adherence levels with maximized non-adherence in ART management by PLWH.