The objective of this study is showing the effect of bird's age on semen quality, semen collection, seminal plasma characteristics and testicular histology on pigeon males, and the potential effect of L-carnitine supplementation on these traits. Forty male pigeons of two ages (1 or 5-years-old) were used in the current study. The pigeons were housed individually and assigned within age, to two L-carnitine treatments (0 or 2 g/L of water) in a 2 x 2 factorial arrangement. There were ten birds per treatment in each age. Collection semen traits, testes mass, sperm parameters, seminal plasma parameters, cloacal mucosa color, donor response to semen collection and testes histology were recorded during the last two weeks of experimental period (10 weeks). The results showed that most of studied traits were depressed with aged birds without L-carnitine supplementation. L-carnitine supplementation to adult and aged birds for 8 weeks significantly increased ejaculate number, collection rate, semen volume, sperm concentration, sperm motility, live sperms, total carnitine in seminal plasma, red cloacal mucosa color percentage, and response to semen collection. Also, L-carnitine supplementation decreased dead sperms, abnormal sperms, seminal plasma total protein, and acid phosphatase activity. Both of L-carnitine supplementation and males' age interacted significantly to influence most of studied traits where the best results were noticed with the adult birds received L-carnitine while the worst records were observed with aged birds without L-carnitine supplementation. Although, absolute and relative testes weights were not affected by either of bird's age or L-carnitine supplementation, the histological examination of testicular tissue of adult or aged birds supplemented with L-carnitine showed a reduction in spermiophage cells and the interstitial cells appeared dark stained indicating high steroid activity. In conclusion, it is recommended that the level of 2g/L L-carnitine could be supplemented to pigeon males to improve semen quality, semen collection,seminal plasma characteristics and testicular histology, especially with aged birds.