Nanofibrillated celluloses have been used in a number of applications: as thickeners, emulsifiers or additives in food, paints and coatings, cosmetics and medical devices, as reinforcing agents in composites due to their high Young modulus. Recently, papermakers have focused on their potential use for enhancing the strength properties of paper. In this study, cationic and anionic nanofibrillated celluloses were prepared by using a bleached sulphite pulp and their adsorption properties and effects on paper strength were investigated. Cationic nanofibrillated cellulose (CNFC) was produced by homogenization of pulp fibres after cationic modification with 3-chloro-2-hydroxypropyltrimethylammonium chloride. Anionic nanofibrillated cellulose (ANFC) was produced by oxidizing fibres with 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO), followed by final disintegration of fibres to nanofibrils by means of a high pressure homogenizer. The adsorption properties of CNFC and ANFC on silicon oxide surface were studied by means of Quartz Crystal Microbalance with Dissipation (QCM-D) in terms of adsorbed mass and viscoelastic properties. The CNFC and ANFC were also tested as additive for enhancing the dry strength of paper. Results showed that the tensile index of paper was higher when CNFC was used together with ANFC, compared with single addition of CNFC to fibre suspension.