CelluloseCellulose is a crucial renewable polymer widely utilized in the biomedical and pharmaceutical industries because of its natural abundance, biocompatibility, biodegradability, non-toxicity, hydrophilicity, antimicrobial properties, and ease of fabrication. Despite its potential, the application of microcrystalline cellulose and its modified derivatives as supports for catalysts and reagents in three-component condensation reactionsThree-component condensation reaction (3C-CR) in pharmaceutical research, particularly in medicinal chemistry and drug manufacturing, is still underexplored and inadequately categorized. This chapter reviews key 3C-CR reactions, including the Betti, Biginelli, Kabachnik-Fields, Hantzsch, Passerini, Povarov, and Strecker reactionsStrecker reaction. Recognizing the significance of green chemistry in sustainable medicinal chemistry, the discussion underscores the role of cellulose-based catalysts andModified Cellulose (MC) modified cellulose-based reagents in these reactions. Additionally, the chapter examines their structural classification, physicochemical properties, and related chemical processes in synthesizing drug-like molecules and innovative cellulose-based biomaterials.