<p>Senescence negatively alters animal fertility and reproductive performance. This study aimed to investigate whether or not L-citrulline could affect testicular morphometry, vascular perfusion, coloration area, steroids, oxidative biomarkers, and semen quality in aged bucks. Hegazi Bucks (<i>n</i> = 14; aged 7.5 ± 0.5 years) were divided into control and treated (injected single dose of L-citrulline) groups and examined at time points (-1, 0, 4, 8, 24, 48, 72, and 96&#xa0;h) before and after injection. Morphometry [testicular length and volume (TV)], Doppler examination [testicular colored area (TCA; pixels), and testicular artery resistive and pulsatility indices (TA.RI and TA.PI)], blood sampling and hormonal analysis [testosterone (T), and estradiol (E2)], nitric oxide (NO), semen evaluation [progressive motility (PM), sperm cell concentration (SCC; 10⁹/mL), viability and morphology (V and M%)], and seminal plasma biomarkers [total antioxidant capacity (TAC), malondialdehyde (MDA), and catalase enzyme concentrations (CAT)] were estimated. The infusion of L-citrulline had no effect on TV. In contrast, TCA levels were higher (<i>P</i> = 0.01) in treated males 24 and 72&#xa0;h after injection. At 24 and 96&#xa0;h, TA.RI and PI declined (<i>P</i> = 0.02). Both E2 and NO levels increased earlier than T concentrations, beginning at 8&#xa0;h, although circulating L-citrulline increased (<i>P</i> = 0.001) at 48&#xa0;h and T concentrations increased (<i>P</i> = 0.02) from 24 to 72&#xa0;h. TAC concentrations were declined, while MDA and CAT were elevated in the treated males. PM % and SCC 10⁹/mL were increased at 24 and 48&#xa0;h, while V and M% were not different. L-citrulline showed transient improvements in testicular vascularization and the hormonal profile of aged Hegazi bucks in relation to the semen quality with oxidative markers. The effects that have been recorded are temporary and only last for 96&#xa0;h, in addition, short term citrulline administration is safe and well tolerated.</p>