Background: Hypertension is a prevalent non-communicable disease and unequivocally one of the most serious health threats of the twenty-first century. The prevention of both immediate and long-term consequences depends on ongoing therapeutic education. Aims: To assess Tunisian hypertensive patients’ knowledge of hypertension and then evaluate the impact of an educational program on knowledge among this population. Methods: A randomized controlled trial was carried out among 639 hypertensive patients in Tunisia. The control group received only basic medical care, while the experimental group acquired additionally an educational program. The data collection tool was a questionnaire that included an information sheet and the Hypertension Knowledge Level Scale (HK-LS). Results: Before to the implementation of the program, only 12.1% of the participants had a good level of knowledge about hypertension (12.8% for the experimental group, vs. 10.5% for the control group, P=0.57). Following the program’s deployment, the rate of good level of knowledge became 63.6% for the experimental group vs. 11.4% for the control group, P<0.001). The results revealed that the experimental group showed a significant amelioration in the total score of the HK-LS: from 58.49 to 76.94%, P<0.0001. In contrast, no significant amelioration was noted in the control group. Concerning the six dimensions of the scale, the amelioration in the experimental group was observed in all dimensions, except the treatment dimension. Conclusion: Overall, the findings indicated low levels of knowledge about hypertension. This kind of approach proved an effective improvement in disease-related knowledge and may be essential for hypertension management.