In recent decades, the role of poly(dopamine) in governing mussel adhesion has been gradually understood and exploited as a novel bio-mimicking adhesion concept. In parallel, the polysaccharide materials present a broad class of functional materials ranging from macro- to nanoscale components with broad variety in chemical structure, morphology and reactivity. The cross-over between both research fields enables the creation of fascinating materials with advanced engineering properties, where the (poly)dopamine serves as a general platform for the functionalization of polysaccharides. In this review, the role of poly(dopamine) in modification of cellulose and nanocellulose materials is discussed by means of several recent examples from literature. A broad variety of applications is presented, including bio-composites, nanoparticles and nanofibers, nanocomposites, hydrogels, aerogels, textiles, adhesives, films and papermaking applications. The review aims at stressing the viability of technical applications against a background of both the chemical and engineering aspects of dopamine-modified cellulose.