Cell division cycle 25 (CDC25) phosphatases regulate key transitions between cell cycle phases during normal cell division, and in the event of DNA damage they are key targets of the checkpoint machinery that ensures genetic stability. Taking only this into consideration, it is not surprising that CDC25 overexpression has been reported in a significant number of human cancers. However, in light of the significant body of evidence detailing the stringent complexity with which CDC25 activities are regulated, the significance of CDC25 overexpression in a subset of cancers and its association with poor prognosis are proving difficult to assess. We will focus on the roles of CDC25 phosphatases in both normal and abnormal cell proliferation, provide a critical assessment of the current data on CDC25 overexpression in cancer, and discuss both current and future therapeutic strategies for targeting CDC25 activity in cancer treatment.