An image forming system includes an image forming apparatus, a sheet feeding apparatus, and a connection device. The connection device is interposed between the image forming apparatus and the sheet feeding apparatus, and connects the sheet feeding apparatus to the image forming apparatus so as to be detachable therefrom. The connection device includes a first exterior portion attached to the image forming apparatus, and configured to surround an access portion by a portion thereof being open, and a second exterior portion attached to the sheet feeding apparatus, fitted to an opening portion of the first exterior portion in a state where the sheet feeding apparatus is mounted on the image forming apparatus via the connection device, and configured to surround the access portion together with the first exterior portion.