Introduction: Testicular torsion is one of the conditions of the acute scrotum that requires immediate surgical intervention. If not recognized at time, it can result of ischemic injuries and testicular loss. Restoration of blood flow is essential to save ischemic tissue, but reperfusion itself paradoxically causes further damage. Seaweed and sponges are considered to be the richest source of bioactive compounds that have antioxidant activity. The antioxidant activity of astaxanthin is 10 times higher than zeaxanthin, lutein, canthaxanthin, β-carotene and 100 times higher than α-tocopherol. Since to date there is no drug given to patients with torsion-detorsion testicular injury, we have investigated the effect of this powerful antioxidant. ----- Objective: The aim of this study was to determine the effect of astaxanthin (ASX) on testicular torsion-detorsion injury in rats. ----- Materials and methods: Thirty-two male Fischer prepubertal rats were divided into 4 groups of 8 individuals. Group 1 underwent sham surgery to determine basal values for histological evaluation. In group 2 (torsion-detorsion group), right testis was twisted at 720° for 90 min. After 90min of reperfusion, the testis was removed. Astaxanthin was administered intraperitoneally at the time of detorsion (group 3) and 45 min after detorsion (group 4) in the treatment groups. Using software ImageJ®, histological morphometric values were measured. ----- Results: MSTD (mean seminiferous tubule diameter) values increase statistically significantly in ASX groups compared to T/D group. MSLD (mean seminiferous lumen diameter) value was statistically significantly lower in the ASX group 3 compared to the T/D group. Epithelial height was statistically significantly higher in ASX groups compared to the T/D group. Tubular area is statistically significantly higher in ASX group 4, while the luminal area is statistically significantly lower in the ASX group 3 compared to the T/D group. Johnsen score was statistically significantly higher in the ASX groups compared to the T/D group. ----- Discussion: This is the first scientific paper to study the effects of a single powerful antioxidant on all morphometric parameters. In previous scientific papers, scientists have mainly measured MSTD and the Johnsen score. ----- Conclusion: By measuring all histological morphometric parameters (mean seminiferous tubule diameter, mean seminiferous lumen diameter, epithelial height, tubular area, luminal area, Johnsen score) it can be concluded that astaxanthin has a favorable effect comparing the treated groups to untreated group.