Microfibrillated cellulose (MFC) was isolated from the byproduct of soymilk, tofu, and okara (soybean residue) using a chemi-mechanical technique. Initially, petroleum ether treatment at 50 °C for 8 h and protease treatment at 50 °C for 2 h were used to remove fat and protein, respectively. A 6 wt% hydrochloric acid solution at a 20 mL/g acid-to-cellulose ratio was applied at 88 °C for 60 min to remove the residual hemicellulose and degrade cellulose. Finally, the sample was gently homogenized at 60 MPa to aid in individualization of the fibers to nano dimension; homogenization for 5 and 25 passes resulted in fibers labeled as MFC-5 and MFC-25, respectively. The amorphous region of okara cellulose was higher than other non-wood fibers. The average diameters of MFC-5 and MFC-25 were within the range of 13 nm to 93 nm and 9 nm to 55 nm, respectively. MFC obtained from okara has potential to reinforce ecofriendly cellulosic nanofibrillated for diverse applications.