Blending of natural rubber (NR) and nanosilica (SiO2) was performed in latex state. The mechanical properties of NR/SiO2 nanocomposites at various filler contents were investigated. The interactions of unvulcanized natural rubber and nanosilica filler were characterized using Fourier Transform Infrared (FTIR)-Attenuated Total Reflectance (ATR) spectroscopy. The relationship between mechanical properties and rubber-filler interaction was discussed.