In this research, convective heat transfer of the argon gas flow through a micro/nano channel with uniform heat flux wall boundary condition is investigated using the direct simulation Monte Carlo (DSMC) method. Both of the hot wall (q(w) > 0) and the cold wall (q(w) < 0) cases are considered. Implementation of wall heat flux in the DSMC method is performed using the recently developed "iterative" technique. Our investigation considers heat transfer behavior in both of slip and transition flow regimes. We investigate the influence of rarefaction, i.e., Knudsen number, and viscous dissipation, i.e., Brinkman number, on the Nusselt number behavior. We use the generalized hard sphere (GHS) collision model to consider accurate variation of the heat conductivity with the temperature. The DSMC solutions for the Nusselt number are compared with different analytical expressions reported in the literature with suitable accuracy through the slip regime. We observe that the dependency of the Nusselt number on the Knudsen number decreases in nanochannels as Knudsen number increases into the transition regime, i.e., Nusselt number approaches nearly a constant value as Knudsen number goes beyond 1. Additionally, it is shown that the Nusselt number is a weak function of the Brinkman number. (C) 2014 Elsevier Ltd. All rights reserved.