Development and optimization of advanced bioink formulations for living tissue-engineered scaffolds remain a challenging task. Herein, a nanofibrillated cellulose (NFC)-composited gelatin methacryloyl (G)/alginate (A) formulation (G/A/NFC100) was prepared for 3D bioprinting of mouse preosteoblasts MC3T3-E1, whereby the G/A formulations with a mixed NFC/microfibrillated cellulose (MFC) and without NFC were included for comparison. The rheological properties of G/A formulation were enhanced by the addition of NFC, as evidenced by a decreased viscosity index characterizing shear thinning behaviour from 0.52 (G/A) to 0.19 (G/A/NFC100). To construct 3D scaffolds with excellent shape fidelity while minimizing shear damage to cells during extrusion, the bioprinting conditions of the formulations were optimized based on the parameter optimization index. The G/A/NFC100 scaffold printed at a printing speed of 2 mm/s and a dispensing pressure of 30 kPa from a 27-gauged nozzle displayed a high shape fidelity (printability index of 0.883). The mechanical stability of the crosslinked 20-layered G/A/NFC100 structures were demonstrated by three consecutive press-relax cycles. The successful bioprinting of mouse preosteoblasts using the G/A/NFC100 formulation translated into an increased cell viability (above 97.64%) up to 21 days post-bioprinting. These results emphasize the exceptional potential of NFC-composited G/A formulation for bioprinting of bone tissue analogues for biomedical applications. In addition, the long-term controlled release of ampicillin (67.42% after 72 h) by G/A/NFC100 scaffolds demonstrates the feasibility of utilizing porous cellulose fibers as drug-delivery carriers to enable multifunctionality in bone tissue repair.