<p>The present study was designed to determine the association between blood perfusion score status at the testicular vascular cone and testicular temperature gradient, as well as semen quality, in dairy bulls during summer. Twenty (<i>n</i> = 20) adult bulls, ten each of Karan Fries cattle (<i>n</i> = 10) and Sahiwal cattle (<i>n</i> = 10) were taken for the experiment. The temperature-humidity index (THI) record was measured daily throughout the experiment to assess the daily summer stress level. Infrared thermography was conducted biweekly to assess the testicular temperature gradient. Color Doppler ultrasonography was performed monthly to evaluate testicular blood perfusion, and semen evaluation was carried out biweekly. Sahiwal bulls have a significantly lower (<i>p</i> &lt; 0.05) percentage area with blood flow at the testicular vascular cone (45.10 ± 2.09) than Karan Fries bulls (50.73 ± 2.59). The mean percentage of progressive motility, sperm viability count, acrosomal integrity, and HOST were significantly higher (<i>p</i> &lt; 0.05) in Sahiwal bulls (75.25 ± 1.31,78.02 ± 1.51, 85.68 ± 0.50 and 66.18 ± 0.71) in comparison to Karan Fries bulls (71.25 ± 1.23, 74.04 ± 0.67, 83.75 ± 0.47 and 64.04 ± 0.34). Testicular temperature gradient was significantly (<i>p</i> &lt; 0.01) positively correlated with percentage area with blood flow, vascularity score, mass motility, progressive motility, sperm viability count, acrosomal integrity, HOST in Karan Fries and Sahiwal bull, whereas it significantly (<i>p</i> &lt; 0.05) negatively correlated with sperm abnormality in both breed bulls. It can be concluded that, in the present study, effective testicular thermoregulation and blood perfusion at the vascular cone emerge as critical markers for assessing and improving semen quality under summer stress. Thus, selecting bulls with superior thermal adaptation can improve reproductive efficiency in dairy herds.</p>