In this work, the effects of the addition of Nb and Al on the microstructures and tensile behaviours of micro-alloyed powder metallurgy (PM) steels were investigated. The microstructure of the micro-alloyed PM steels was examined by light microscope, SEM, XRD, XRF and EDS. The results indicated that the addition of (0.1, 0.15 or 0.2) % of Nb-Al increases the yield strength (YS) and the ultimate tensile strength (UTS) of the PM sintered steels. Elongation also tends to improve with an increasing Nb and Al content. In addition, the Nb and Al limit the grain growth during austenitization.