Granular cell tumour (GCT), which is a rare benign soft tissue neoplasm, is mostly found in the skin and soft tissue but may develop anywhere in the body. There are less than 10 reported cases of mediastinal GCTs in the current literature. Furthermore, colonic GCTs have recently gained attention due to the increased public awareness on the importance of colonoscopy screening. We report a case of a 52-year-old woman diagnosed incidentally with synchronous GCTs of the mediastinum and the hepatic flexure on her routine screening for post-operative follow-up for status-post right modified radical mastectomy due to a T2N1M0, Stage 2B breast cancer.