Hypertension (high blood pressure) is one of the most common health conditions. When your blood pressure is high for a long term, it can cause health problems, such as heart disease. In addition to the main methods of treatment, there are various methods of adjuvant therapy, one of the most common of which is hydrotherapy. In this review study, we examined the effects of hydrotherapy, balneotherapy, and spa therapy on blood pressure. We searched the PubMed/MEDLINE, Web of Science, Scopus, and Science Direct databases until April 2022 using related keywords. In summary, the current study shows that different hydrotherapy methods may improve blood pressure. Hydrotherapy as one of the adjunctive therapy methods can be effective in lowering blood pressure. Blood circulation is smoothed by the warmth of the water. This improvement may be achieved by regulating heart rate, releasing hormones that control blood pressure, or regulating the activity of baroreceptors or chemoreceptors. In addition to using medications, hypertension patients also use non-pharmacological approaches in their care, including hydrotherapy, balneotherapy, and warm water foot soaks performed at home. Although several lines of evidence show the potential effects of hydrotherapy, balneotherapy, and spa therapy on blood pressure, many clinical trials are needed.