The thermal diffusivity of nanofluids containing silver nanorods in cetyltrimethyl ammonium bromide micelle has been investigated by measuring the time constant of transient thermal lens. The important observation is that the nanofluids exhibits improved thermal diffusivity in comparison to the base fluid. Also, it is found that, the effective thermal diffusivity of nanofluids with rod-shaped nanoparticles is greater than that of nanofluid with spherical nanoparticles. This is explained on the basis of the empirical shape factor by Hamilton Crosser model. Several factors such as chemical environment, formation of nanolayer around the particle surface, nanolayer thickness and interfacial resistance are also considered to explain the results. These results are discussed in connection with the possibility of using rod-shaped silver nanoparticles to enhance the thermal diffusivity of heat transfer fluids. ► Thermal diffusivity of nano-fluids composed of rod-shaped silver nanoparticles is investigated. ► Rod-shaped nanoparticles improve the heat diffusion in the base fluid more efficiently than the spherical nanoparticles. ► Various factors like shape of the nanoparticles, chemical environment etc. are considered to explain the results.