We provide new information about CHEK2 mutation in association with a rectal neuroendocrine tumor (NET). A 67-year-old Caucasian woman diagnosed with estrogen receptor positive ductal carcinoma in situ breast cancer underwent genetic testing, revealing a CHEK2 mutation that prompted her to have a colonoscopy. This revealed a polyp with immunohistochemical staining positive for markers classically associated with NETs. Six-month follow up surveillance colonoscopy after initial polyp removal found no evidence of recurrence. While the CHEK2 mutation is known to be associated with adenocarcinomas, there is only one other reported case of its association with NETs.