Monosodium glutamate (MSG), a commonly used food ingredient, has been reported to induce testicular dysfunction. This study aimed to evaluate the therapeutic potential of hesperidin (HESP), a citrus flavonoid, against MSG-induced testicular dysfunction, comparing it to sildenafil citrate (Sc). This investigation focused on oxidative stress, inflammation, apoptosis, histological alterations, spermatogenesis, steroidogenic enzyme expression, and reproductive hormone levels. Twenty-four adult male rats were divided into four groups: a negative control group (n = 6) and three MSG-treated groups (n = 18) that received MSG (1 g/kg/day) for four weeks, followed by either no treatment (positive control), HESP (200 mg/kg/day), or Sc (5 mg/kg/day) for another four weeks. Oral MSG exhibited significant reductions in gonadosomatic index, sperm parameters, and reproductive hormones, accompanied by downregulation of steroidogenic genes, severe histological damage to testicular tissues, and marked elevation in oxidative stress, inflammation, and apoptosis markers. HESP significantly improved sperm count (88 %) and motility (59 %), while reducing sperm abnormalities (34 %), outperforming Sc, which decreased sperm abnormalities by 15 %. Further, HESP significantly reduced inflammatory markers, including nuclear factor-kappa B, TNF-α, interleukin-1β, and interleukin-6 compared to MSG, outperforming Sc. HESP also demonstrated superior efficacy in reducing Bax by 41 % and increasing Bcl-2 by 68 %, while Sc reduced both by 27 % and 28 %, respectively. However, Sc also demonstrated superior efficacy in reducing malondialdehyde levels (67 %) and increasing catalase activity by 645 %, exceeding the effects of HESP (34 and 413 %, respectively). Overall, HESP outperformed Sc by reducing oxidative damage, inflammation, and apoptosis, while enhancing steroidogenesis, spermatogenesis, and reproductive hormones in MSG-treated rats.