According to the World Health Organization (WHO), colorectal cancer (CRC) ranks third in morbidity (∼2 million cases) and second in mortality (∼1 million deaths) [1]. Several risk factors are implicated in the development of CRC, including familial, hereditary, environmental, and lifestyle-related factors [2]. Infectious pathogens, including parasites, have been reported to account for 16–18 % of all malignancies worldwide [3,4]. Few studies have reported an association between parasites and the development of CRC [[5], [6], [7], [8]]. Cryptosporidium and Blastocystis, as prevalent enteric parasites, may pose serious challenges in CRC patients receiving chemotherapy due to their localization in the gastrointestinal tract [[5], [9]]. Moreover, Cryptosporidium was detected in 21 % of biopsies from patients with newly diagnosed colorectal neoplasia by PCR before any treatment, compared to 7 % of biopsies from patients without gastrointestinal neoplasia but with persistent gastrointestinal symptoms [10]. Regarding Blastocystis hominis (B. hominis), a possible association with CRC has been suggested, indicating its potential influence on CRC progression; however, further studies are required to confirm this risk [5,11]. Few case reports have described gastrointestinal cancer associated with Strongyloides stercoralis (S. stercoralis) infection, suggesting that the parasite may be a risk factor for gastrointestinal malignancy [12,13]. Carcinogenesis related to infection is generally attributed to three primary mechanisms: chronic inflammation caused by the persistence of an infectious agent in the host, insertion of oncogenes into the host genome, and reduced immune surveillance due to immunosuppression [14]. Accordingly, this study aimed to determine the prevalence and association of B. hominis, Cryptosporidium spp., and S. stercoralis in patients with CRC in tertiary care centers.