This study aimed to investigate the impact of multi-sources medications on adherence to antihypertensive pharmacotherapy. 604 outpatients with established hypertension from eastern Taiwan were enrolled in this study. A cross-sectional study was used to measure blood pressure and physiological parameters, and a structured questionnaire to all hypertension outpatients. The three adherence groups had significant differences in the sources of medications (P <0.05). Multiple medications sources have a significant adverse effect on adherence (β = -1.06, P <0.01). Adherence is a predictor of SBP (β = -0.60, P = 0.03), DBP (β = -0.32, P = 0.04) and MAP (β = -0.41, P = 0.02). Multiple medications sources are associated with non-adherence with antihypertensive pharmacotherapy, which adherence was found to predict blood pressure control.