The causality from outsourcing, defined as the procurement of inputs from outside the boundaries of the firm, to productivity is tested for a large panel of Irish manufacturing firms. Theory suggests that as firms outsource more 'non-core' activities to specialized providers, productivity due to the firm benefiting from cheaper or higher-quality inputs and from reallocation of resources towards higher value-added activities. The international outsourcing case adds another dimension in the form of input variety, quality and technological embeddedness. I test the above hypothesis using a "System GMM" estimator to control for endogeneity in the panel and allow for a lagged dependent variable to be a regressor. International outsourcing is found to lead to productivity gains, but upon closer inspection it seems that firms? international orientation and type of industry both matter.