To evaluate the relationship between varicocele and ankylosing spondylitis (AS) via color duplex sonography (CDS). Thirty male patients (age range 18–40 years, mean age 30.27 years) with AS and 30 male healthy controls (age range 20–36 years, mean age 27.23 years) were evaluated for varicocele using CDS. Vein diameter in right and left pampiniform plexus (PP) in the AS group was significantly higher than in the control group (p < 0.001 and p = 0.003, respectively). The incidence of varicocele was observed as 33.3 % in the AS group and 10 % in the control group. However, the difference was statistically significant (p = 0.028). The rate of right, left, and bilateral varicocele was 3.3 % (1 patient), 23.3 % (7 patients), and 6.6 % (2 patients), respectively, in the AS group, versus 0, 10, and 0 % in the control group (p = 1.000, p = 0.166, and p = 0.492, respectively). The incidence of varicocele in AS patients is higher than in control subjects, and the difference is statistically significant. Therefore, varicocele must be taken into consideration and investigated in patients with AS.