High expression of cell division cycle 20 homolog (CDC20), a key component of the spindle assembly checkpoint (SAC), has been reported in various malignancies and plays a vital role in tumorigenesis and progression. The goal of this study was to evaluate the utility of CDC20 immunostaining in a wide range of malignant tumors. CDC20 immunohistochemistry was evaluated in normal tissues and compared to the most frequently occurring malignant tumors in these tissues (bladder, breast, cervical, colonic, endometrial, gastric, head and neck, liver, lung, ovarian, pancreatic, prostatic, renal, thyroid carcinomas, and testicular seminoma). Normal/non-neoplastic tissues showed positive CDC20 expression in 19.44 % of all examined cases. CDC20 staining was negative in normal and non-neoplastic tissues from the bladder, cervix, liver, stomach, and thyroid. From the all malignant tumors examined 55.7 % showed high CDC20 expression while low expression was found in 44.3 %. High expression of CDC20 was associated with high tumor grade in the bladder (p = 0.027), cervical (p = 0.032), colonic (p = 0.026), endometrial (p = 0.016), gastric (p = 0.033), liver (p = 0.028), ovarian (p = 0.044), prostatic (p = 0.040), and renal (p = 0.048) carcinomas. There was a significant correlation between high CDC20 expression and advanced tumor stage in carcinoma of the breast, colon, endometrium, and prostate (p = 0.021, p = 0.040, p = 0.047, p = 0.031, respectively). CDC20 expression may be useful as a biomarker of tumor prognosis and as a therapeutic target of human cancer.