The objectives of this study were, firstly, to assess medication adherence and, secondly, to evaluate the relationships between medication adherence and symptoms, disease activity, and patient-reported outcomes in patients with newly diagnosed primary Sjögren disease (pSjD). In this prospective observational cohort study, 54 patients with newly diagnosed pSjD were enrolled in a tertiary rheumatology clinic. Forty patients (74.1%) were reassessed after a mean follow-up of 21.36 ± 4.79 months. Medication adherence was evaluated using the Compliance Questionnaire for Rheumatology-5 (CQR-5), classifying patients as low or high adherence. Disease activity, symptom burden, psychological symptoms, fatigue, functional status, health-related quality of life, and medication beliefs were evaluated using ESSDAI, ESSPRI, HADS, fatigue severity assessment, HAQ, SF-12, and the Beliefs about Medicines Questionnaire (BMQ). The necessity-concern differential (NCD) was calculated as the BMQ-specific necessity score minus the concern score. Logistic regression analysis was exploratory. The cohort was predominantly female (52/54, 96.3%), with a mean age of 49.7 ± 9.5 years. At follow-up, 16 patients (40%) were classified as low adherence and 24 (60%) as high adherence. Baseline clinical and sociodemographic characteristics were comparable between groups. ESSDAI scores remained low and stable over time, and ESSPRI increased modestly in both groups without significant between-group differences. Psychological status, fatigue, functional status, and quality of life were similar across adherence categories. Specific necessity scores were numerically higher in high-adherence patients (3.37 ± 0.79 vs. 3.04 ± 1.06; p = 0.267), whereas concern scores tended to be higher in low-adherence patients (3.46 ± 0.92 vs. 3.07 ± 0.63; p = 0.115). The NCD was significantly lower in the low-adherence group than in the high-adherence group (− 0.43 ± 1.16 vs. 0.30 ± 0.96; p = 0.038). In exploratory logistic regression, higher NCD was associated with high adherence (OR 1.95, 95% CI 1.01–3.76). In patients with newly diagnosed pSjD, low medication adherence was frequent and was associated with patients’ necessity-concern balance rather than clinical disease activity or patient-reported burden. Because adherence and medication beliefs were assessed at the same time point and CQR-5 has not been specifically validated in pSjD, these findings should be interpreted as exploratory and non-causal.