In this work, effects of different tool pin profiles of flat and tapered shoulder geometries on the peak temperature in friction stir welding are investigated analytically. The developed models used for the analytical investigations considered the welding process as a combination or mixture of the pure sliding and the pure sticking. From the results, the amount of heat generation and the peak temperature are directly proportional to the number of edges in the pin profiles in such a way that the heat generated and peak temperature in the profiles increases from the triangular pin profile to hexagonal pin profile. Also, the rate of heat generation and the peak temperature in flat shoulder are greater than in tapered/conical shoulder. The results in this work are validated with experimental and the past theoretical results and good agreements are achieved.