A sheet processing apparatus includes: a center-folder to perform a center-folding process on a sheet bundle including multiple sheet materials; a back-crimp binder to: form a back portion on the sheet bundle subjected to the center-folding process; and perform a crimp-binding process on the back portion; and a controller configured to: cause the center-folder to perform the center-folding process; and cause the back-crimp binder to perform the crimp-binding process on the back portion while forming the back portion on the sheet bundle in the crimp-binding process.