Silver nanoparticles (AgNPs) were rapidly synthesized using sugar beet leaf extract, and the formation of nanoparticles was observed within 3 h. AgNPs uniformly were reacted onto the surface of nanocrystal cellulose (NCC) via complexation leading to NCC/AgNPs, (NCC/Ag) nanohybrids with varying concentration of AgNPs (0, 1, 4, 8, and 10%) along with 2 wt% of NCC. Polyurethane (PU) and PU/N-CC/AgNPs were synthesized via in situ polymerization by varying the concentration of AgNPs (0, 1, 4, 8, and 10%) along with 2 wt% of NCC. The results recorded from transmission electron microscopy and X-ray diffraction support the biosynthesis and characterization of AgNPs. The effects of NCC/AgNP content on the physicomechanical properties involving density, tensile behavior, and surface hardness of the nanocomposites have been measured. The effects of the NCC/AgNP content on the viscoelastic properties of PU were investigated using dynamic mechanical analysis (DMA). From DMA analysis, it has been noted that the incorporation of NCC/AgNPs leads to a change in T g . The PU and PU/NCC/AgNP nanocomposites were employed as an excellent adsorbent for the adsorption of nickel (II) and lead (II) ions. The results indicated that ion adsorption basically relies on adsorbing time, solution pH, initial nickel and lead concentration, and adsorbent dosage. POLYM. COMPOS., 40:4004-4012, 2019.