Biochemical additives encompass materials added to the papermaking operation that are derived from biological origins. Other than starch, the majority of the biochemical additives currently used in the paper industry are enzymatic. Enzymes are protein structures that speed a particular chemical reaction. The enzymes are not consumed during the reaction and can be used repeatedly. The enzymes used in the paper industry typically target one of the four major components of wood: cellulose, hemicellulose, lignin or extractives. Enzymes have been used industrially to aid in bleaching, reduce pitch, enhance strength, alter pulp freeness, and aid in paper machine cleaning. This review focuses on the use of enzymes in the papermaking operation, but also addresses the use of enzymes in other areas of the pulp and paper mill. There has also been considerable work in the use of fungus for improving both mechanical and chemical pulping operations. This is considered a separate topic and is only brieﬂy addressed in this review. The future of biochemical additives may extend well beyond the current use of enzymes and a few notes on potential application are given.