We report here a monolithic all-fiber laser oscillator with femtosecond-written FBGs and side-pumping coupler. The splice-free resonant cavity is realized by directly writing a pair of fiber Bragg gratings (FGBs) into an ytterbium-doped fiber (YDF) based on the femtosecond laser phase mask scan method. Furthermore, a (2+1)×1 side-pumping coupler is fabricated in the same YDF by the taper-fused method. When pumping with two 976 nm laser diodes (LD), a maximum output power of 1218 W is realized at the 1070 nm, corresponding to the optical-optical conversion efficiency of about 71%. This work displays an extremely compact and stable fiber laser oscillator, which is of great significance to the development of high power fiber lasers.