Background: Hypertension (HTN) is a serious medical disease and the main cause of cardiovascular diseases and premature death worldwide. Purpose: The purpose of this study was to investigate the effectiveness of online mindfulness-based stress reduction (OMBSR) on systolic blood pressure (BP), diastolic blood pressure (BP), and heart rate (HR) in patients with diagnosed hypertension. Methods: The present study was a randomized clinical trial based on the pretest, posttest, and follow-up design. Thirty-four patients were included in the study by the Purposive Sampling method and randomly assigned to two groups of OMBSR and control. SBP, DBP and HR were measured the research data were analyzed using repeated measures ANOVA and Bonferroni test using SPSS[subscript 26] software. Results: The results showed that the "posttest" and "follow-up" scores of SBP, DBP, and HR in the mindfulness group decreased significantly compared to the pretest scores (P < 0.001); while there was no significant difference between the scores of the control group at different times. Discussion: OMBSR may have the potential to affect SBP, DBP, and HR, via treatment adherence in patients with hypertension. Translation to Health Education Practice: Health educators may want to use OMBSR as a supplement to drug therapy solving problems related to patients with hypertension.