In this investigation , natural convection heat transfer from a heater placed on the bottom of a square enclosure with adjacent inclined wall was carried out . The inclined wall has a constant lowtemperature , while the heater element has a constant high temperature ,and the remaining walls are insulated . The working fluid used is air with Prandtl number (Pr=0.72) . The governing equations of the problem are solved numerically by using finite differencemethod . The numerical solution is presented for various Rayligh numbers,Ra(103-105) , with different dimensionless parameters as length of heater (Yh¬) (0.1,0.3,0.5), different locations of the heater (Xh) (0.25,0.5) and inclination angle of inclined cold wall (10o, 20o, 30o). The results are presented by isotherms and streamlines to show the behavior of the flow and temperature distribution .While the numerical results of heat transfer are presented by average Nusselt number and local Nusselt numbers at right , left and top sides of heater.The results show the effect of dimensionless parameters on heat transfer and Nusselt number.It is observed that the Nusselt number increased by increasing Raylig number , heater length , inclination angle of cold wall and where the heater is near the cold wall (Xh=0.5).