The viscoelastic and flow properties of aqueous Laponite/TEMPO-oxidized nanofibrillated cellulose (TEMPO-NFC) systems are investigated with the aim to study the effect of content and proportion of both components on the properties. Both Laponite and TEMPO-NFC aqueous dispersions can find numerous applications in different fields (from industrial to biomedical one) due to their structural and rheological properties. The most important effects of blending are observed at low Laponite fractions, also with qualitative changes in the shape of the flow curves and mechanical spectra. Positive synergistic effects are ascribed to the interpenetration and electrostatic interactions between TEMPO-NFC fibrils and Laponite nanodisks. These mechanisms are more effective in Laponite-poor blends when a minority of clay nanoparticles and its aggregated forms are distributed within the nanocellulose matrix, acting as bridging agents between polymer nanofibrils. The synergistic effects are compared to those observed for Laponite blends with a nonionic biopolymer, scleroglucan.