As green tea is being consumed in larger amounts, more green tea waste is being produced. Following extraction, several bioactive compounds may exist in the waste including polyphenols and amino acids. It was found that an Aspergillus niger cellulase treatment of green tea waste increased the extractability of various nutritional and functional components after pretreatments with various extraction solvents such as cold water (CW), hot water (HW), sulfuric acid (SA), hydrochloric acid (HA), and methanol (Me). After the residue was treated with cellulase from Aspergillus niger, the amounts of polyphenols, total catechins, and reducing sugars in the HW extract were increased by 64.6, 941.2, and 350.9%, respectively. In particular, levels of epigallocatechin, epicatechin, and gallic acid were significantly enhanced compared to those in the nontreated control. However, protein extraction was not significantly affected, and cellulase treatment was not more efficient for caffeine extraction compared to phenolic extraction. Among the four extraction solvents, HW and SA showed relatively higher extractabilities as compared to the other groups (CW, HA, and Me). These results indicate that cellulase from A. niger can increase the extractability of green tea waste when combined with certain solvent pretreatments. Consequently, the residual functional compounds and essential nutrients from cellulase-treated green tea waste have the potential to be applied in the production of new functional foods.