Possible causes of yellow semen in men: 1. If you have not ejaculated or have not discharged semen for a long time, the phenomenon of yellow semen will occur. At this time, semen appears viscous and yellowish, while there is no abnormal feeling of ejaculation, no local pain, and no abnormal smell of semen. This is a normal physiological phenomenon that does not require excessive attention or any treatment. 2. If infection occurs in the seminal tract or in the seminal vesicles. This is the time when pus can appear mixed in the semen, and the semen is yellowish, accompanied by bad odor and other odors, and can also be accompanied by pain during ejaculation or burning in the urethra and other symptoms. If an abscess is formed in the seminal vesicles, it may be accompanied by painful swelling in the perineal area or a constant urge to defecate. An examination of the seminal vesicles or seminal tract, such as a CT or ultrasound, is required. It is also necessary to take semen for bacterial culture and give anti-infection treatment after confirming the infection.