“Shangshida NO.5” is a giant embryo mutant resulting from giant embryo gene (GE) dysfunction in “Chao2‐10” rice. Here, we compared the antihypertensive effects of “Chao2‐10” brown rice (C2‐10), “Shangshida NO.5” brown rice (GER), and pre‐germinated “Shangshida NO.5” brown rice (PGER) in spontaneously hypertensive rats (SHR). Male SHR at 6 weeks of age were divided into four groups and were fed with (a) a control diet (control), (b) a 40% C2‐10‐supplemented diet (C2‐10), (c) a 40% GER‐supplemented diet (GER), or (d) a 40% PGER‐supplemented diet (PGER) for 8 weeks, and their physiological and biochemical parameters were measured. The results showed that the C2‐10‐, GER‐, and PGER‐supplemented diets significantly decreased systolic blood pressure (SBP) and diastolic blood pressure (DBP) during the experiment. At the end of the experimental period, the SBP and DBP of the C2‐10, GER, and PGER groups were 7.6, 23.3, and 31.1 mmHg and 9.8, 21.1, and 29 mmHg lower than those in the control group, respectively, suggesting the GER and PGER diets were better able to inhibit blood pressure elevation than the C2‐10 diet. The serum creatinine levels in the C2‐10, GER, and PGER groups and the blood urea nitrogen content in the PGER group were significantly lower than those of the control group, indicating that C2‐10‐, GER‐, and especially PGER‐supplemented diets improved renal function. In addition, the antioxidant activity of the C2‐10 group and especially of the GER and PGER groups also improved. The above results suggest that “Shangshida NO.5” rice, particularly pre‐germinated rice, is a good dietary supplement for preventing the development of hypertension.