Objective: Polyethylene terephthalate (PET) is a material that is most commonly used for production of clear plastic bottles. Adenomatous polyposis coli (APC) and β-catenin have been related with cancer. Aim was to investigate the effects of PET bottled water samples that were exposed to sunlight and hot water on zebrafish embryos. Moreover the effects of these water samples on APC knockdown zebrafish embryos were also evaluated.Methods: Phthalate concentrations in water samples were determined using ELISA. Immunohistochemical method and RT-PCR were used to analyse the expressions of proliferative cell nuclear antigen (PCNA), β catenin, Wnt 3a and Gsk3β. Biochemical parameters were measured using spectrophotometric methods. Vitellogenin concentrations were measured using ELISA and apoptotic cells were evaluated by Acridine Orange staining.Results: Increased PCNA, β-catenin, Wnt 3a, Gsk3β expressions, vitellogenin, nitric oxide, apoptosis and impaired oxidant-antioxidant balance were observed in the exposure groups with these increases being more profound in APC knockdown groups.Conclusion: APC knockdown embryos were more prone to the deleterious effects of water samples used in this study.