Conjugate heat transfer in laminar tube flow with convective boundary conditions is considered analytically. The steady state problem involving two-dimensional wall and axial fluid conduction is solved using separation of variables for a thick walled cylindrical pipe. The effects of the wall thickness, external Biot number and wall-to-fluid thermal conductivity ratio are investigated on the heat flux, fluid bulk and wall temperatures. Results are presented for the cases when the wall thickness is between 0.1 and 2, Biot number ranging between 0.1 and 10, and the ratio of wall-to-fluid thermal conductivity between 3 and 100. These parameters are found to significantly affect the heat transfer characteristics at the thermal entrance region, for instance, increase in wall thickness results in reduced heat flux while increase in Biot number and the ratio of the wall-to-fluid thermal conductivity result in increased heat flux. Decrease in wall thickness, increase in both Biot number and the ratio of the wall-to-fluid thermal conductivity correspond to decreased fluid bulk and wall temperature profiles. (C) 2014 Elsevier Ltd. All rights reserved.