This paper aims at investigating the effects of weld nugget size and expulsion on the mechanical properties of low carbon steel resistance spot welds using tensile-shear test. Mechanical performance of spot welds are described in terms of failure mode, peak load and failure energy obtained from the tensile-shear test. The effects of voids and porosity as well as electrode indentation associated with expulsion on the peak load and failure energy of spot weld are discussed. Results showed that although expulsion does not reduce load carrying capacity of spot welds, it decreases their energy absorption capability. This can be attributed to the change in the failure location of the base metal in expulsion free welds to fusion zone/heat affected zone boundary in expulsion-experienced welds.