Background and Aim: Seasonal variations among geographical regions could influence pigeon semen quality differently. This study aimed to determine the seasonal effect on semen availability and quality of racing pigeons in Thailand to understand and improve breeding management in the country. Materials and Methods: Semen was collected from six fertile captive pigeons once a week during summer (March-June), monsoon (July-October), and winter (November-February) during 2019-2020. The success rate of semen collection and semen quality was determined in each season--by which changes in average temperature, humidity, and photoperiod were obtained. Results: Comparable success rates of semen collection were acquired among different seasons, while varied semen qualities were revealed. The percentages of total motility and progressive motility score of sperm were significantly lowest in summer (66.35 [+ or -] 3.40 and 3.88 [+ or -] 0.15, respectively) compared to monsoon (85.45 [+ or -] 2.91 and 4.67 [+ or -] 0.10, respectively) and winter (79.29 [+ or -] 1.96 and 4.37 [+ or -] 0.10, respectively), while its concentration (*109 sperm/mL) and outputs (*106 sperm) were significantly highest in winter (7.62 [+ or -] 0.54 and 91.44 [+ or -] 10.83, respectively) compared to summer (4.23 [+ or -] 0.41 and 48.45 [+ or -] 6.35, respectively) and monsoon (3.57 [+ or -] 0.30 and 51.45 [+ or -] 7.21, respectively). Besides, semen samples collected from birds housing at an average temperature of Conclusion: Winter was regarded as the best season contributing the best semen quality, while summer was the worst. Due to the fluctuation of temperature during summer and winter, the seasonal temperature was implied as the major factor contributing to changes in sperm quality of racing pigeons in Thailand. Keywords: humidity, photoperiod, pigeon semen quality, temperature, Thailand.