Purpose: To determine knowledge regarding hypertension, adherence to medication and HealthRelated Quality of Life (HRQoL), and their associations in hypertensive patients in Pakistan. Methods: A cross-sectional study was conducted among 384 hypertensive patients attending a tertiary health care public sector hospital in Islamabad, Pakistan. Data were collected using knowledge questionnaire regarding hypertension, Morisky Medication Adherence Scale, and EuroQol (EQ-5D) scale. Results: The mean systolic and diastolic blood pressures of the 384 patients were 140.39 ± 15.485 and 88.74 ± 10.683 mmHg, respectively. The coefficient of correlation between knowledge regarding hypertension and adherence was 0.638 (p < 0.001), showing a positive association. The correlation coefficient between knowledge and HRQoL was 0.709 (p < 0.001), suggesting a good association. The correlation coefficient between adherence to medication and HRQoL was 0.545 (p < 0.001), which indicated a positive correlation. Conclusion: These results indicate that there are statistically significant associations between hypertension knowledge and HRQoL, hypertension knowledge and medication adherence, and between adherence and HRQoL in the hypertensive patients studied.