Thermal conductivity enhancement in nanofluids, which are liquids containing suspended nanoparticles, has been attributed to localized convection arising from the nanoparticles' Brownian motion. Because convection and mass transfer are similar processes, the objective here is to visualize dye diffusion in nanofluids. It is observed that dye diffuses faster in nanofluids compared to that in water, with a peak enhancement at a nanoparticle volume fraction, ϕ, of 0.5%. A possible change in the slope of thermal conductivity enhancement at that same ϕ signifies that convection becomes less important at higher ϕ. The enhanced mass transfer in nanofluids can be utilized to improve diffusion in microfluidic devices.