The present study aimed to develop a fermented food (idli) with enhanced γ-aminobutyric acid (GABA) and angiotensin I-converting enzyme (ACE) inhibitory properties using a GABA-producing fungus. Aspergillus oryzae NSK fermented idli batter and GABA was maximized (451.7 mg kg-1) in 120 h. The ACE inhibitory, 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radical scavenging and nitric oxide radical scavenging activities increased to 41.8%, 1.9 and 0.6 μmol trolox equivalent antioxidant capacity (TEAC) per gram in 120 h, respectively. In contrast, phytic acid and trypsin inhibitor activities decreased to 3.01 g kg-1 and 30.8 mg kg-1, respectively. The systolic blood pressure of spontaneously hypertensive rats in the fermented idli diet group was lower than those fed a plain idli diet. Lipid peroxidation in the plain idli diet group was significantly higher, whereas superoxide dismutase and glutathione reductase activities were significantly lower. The expression of genes ET-1, HSP70, NF-κB and iNOS in the aorta of SHRs that received GABA-containing diets was down-regulated between 2.2 and 3.8 fold. The production of GABA-enriched foods can be a promising approach to lower the blood pressure of spontaneously hypertensive rats.