Background Chronic hypertension (CH) and high arterial stiffness (AS) increase the risk of complications during pregnancy, such as superimposed preeclampsia and low fetal growth. Objective To evaluate the impact of hydrotherapy, a non-pharmacological treatment strategy, on AS in pregnant women with CH. Methods Cross-sectional study evaluating the effect of a standardized hydrotherapy session on AS in pregnant women with CH and controls. We used the device Mobil-O-Graph® NG to measure blood pressure (BP), heart rate (HR), and AS before and after a hydrotherapy session involving stretching, warming up, strengthening, and relaxation. The level of significance adopted in the statistical analyses was 5%. Results We evaluated 36 pregnant women, including 12 with hypertension (HG) and 24 controls (CG), aged 30.4 ± 4.8 years and at 29.2 ± 3.3 gestational weeks. Hydrotherapy promoted in both groups a significant reduction in AS assessed by the augmentation index at a HR of 75 bpm (AIx@75) (HG: 28.8 ± 7.3%, before; 22.4 ± 6.9%, after; p = 0.024; and CG: 29.1 ± 7.4%, before; 22.9 ± 6.6%, after; p = 0.001), as well as a reduction in HR (HG: 93.4 ± 11.8 bpm, before; 82.4 ± 10.0 bpm, after; p < 0.001; and CG: 91.4 ± 13.4 bpm, before; 81.5 ± 12.6 bpm, after; p < 0.001), but a nonsignificant reduction in BP. Conclusion We demonstrated that a hydrotherapy session acutely reduces AS assessed by AIx@75, and may represent a potential non-pharmacological strategy to prevent maternal and fetal complications in pregnant women with CH. (Arq Bras Cardiol. 2020; [online].ahead print, PP.0-0).