Previous studies have demonstrated that a natural product of celery seeds, 3‑n‑butylphthalide (NBP), has significant antihypertensive effects that are widely utilized in Chinese traditional medicine. The present study aimed to investigate the effects of NBP on hypertensive nephropathy, as well as the mechanisms underlying this disease in spontaneously hypertensive rats (SHRs). SHRs were treated orally with saline, NBP (15 or 30 mg/kg) or losartan (10 mg/kg) daily for 20 weeks, during which time blood pressure was measured every four weeks. At the end of the 20‑week treatment, blood and urine samples were collected for biochemical analysis, and kidney tissues were obtained for histopathological analysis and immunohistochemistry. Enzyme‑linked immunosorbent assays and western blotting were used to analyze the expression of transforming growth factor (TGF)‑β1 in blood and kidney tissues, respectively. The results showed that NBP effectively attenuated progression of hypertensive nephropathy by decreasing urinary albumin excretion and blood urea nitrogen levels. It significantly decreased blood pressure (although less markedly than losartan) and the incidence of glomerulosclerosis. In addition, it alleviated tubular impairment and significantly decreased oxidative stress, as well as the expression of pro‑inflammatory cytokines and TGF-‑β1 in kidney tissues. In conclusion, the results suggested that NBP may slow the progression of hypertensive nephropathy by a variety of mechanisms.