The aim of this study is to computationally and experimentally investigate the heat transfer and pressure drop characteristics of an offset-strip fin. In the present study, experiments are conducted at the range of Reynolds number from 150 to 3500 and a 3-D numerical domain, which is investigated as a conjugate problem, is created for finite volume computations. The computations are conducted by assuming that the flow in the offset-strip fin channels is steady and laminar at the range of Reynolds numbers from 200 to 5000. In this thesis, the effects of the flow behaviors in the offset strip fin channels on Colbourn j factor, which is the non-dimensional form of heat transfer coefficient, and fanning friction f factor, which is the non-dimensional form of pressure drop, are investigated. Also, the heat transfer boundary conditions and the Prandtl numbers of the fluids are kept different for these fins in order to see the effect of those.The effect of Prandtl number is investigated by using air, 0.707 < Pr < 0.71 and water, 2 < Pr < 4.35 and ethylene glycol, 94 < Pr < 138. The effect of the thermal boundary conditions is investigated by using constant heat flux and uniform temperature. Moreover, all results are compared with Kays and London.s experiments (1964) and also the results of Manglik and Bergles.s correlations (1995). The results show a very good agreement between the results of Kays and London (1964) and of Manglik and Bergles.s correlations (1995). It is also observed that results obtained from the two alternatives for the thermal boundary condition are very close to each other. According to obtained results, it is concluded that our computational results from laminar flow assumption and experiments are reliable at almost all the range of Reynolds numbers studied.