To investigate the ameliorative effects and potential mechanisms of a Pumpkin Seed Oil and Lycopene Oleoresin Composition (POSL), alone and in combination with different doses of phytosterol esters, on benign prostatic hyperplasia (BPH) in rats, a BPH model was established in SD rats by castration combined with subcutaneous injection of testosterone propionate. The animals were allocated to a sham-castration group, a model control group, a positive drug group, a POSL group, and POSL combined with low-dose (PSM) and high-dose (PHS) phytosterol ester compound groups. The prostate index, inflammatory cytokine levels, and histopathological findings and scores were determined, and bladder as well as hepatic and renal function indices were assessed concurrently. The results showed that, compared with the model control group, prostate wet weight and prostate index were significantly reduced in all compound groups, prostatic glandular hyperplasia was alleviated, and inflammatory cytokine levels were decreased. In the PSM group, the inhibition rates of the increases in prostate wet weight and prostate index were 73.13% and 62.76%, respectively; TNF-α and IL-6 levels decreased by 34.73% and 43.85%, respectively; and the bladder index decreased by 20.05%. No marked abnormalities in hepatic or renal function or in routine urinalysis indices were observed in any group. In conclusion, POSL and its compound formulations with phytosterol esters can ameliorate BPH and bladder compensation in rats, and the underlying mechanism may be associated with attenuation of the inflammatory response and inhibition of the abnormal proliferation of glandular epithelial and stromal cells, thereby providing a theoretical basis for the development of related functional foods.