This study examines how different forms of foreign direct investment (FDI) affect firm performance. Using newly linked administrative microdata from Statistics Canada, we analyze how inward and outward FDI—distinguished by their horizontal (market-seeking) and vertical (efficiency-seeking) orientations, and by whether they involve developed or developing partner countries—shape firm-level productivity outcomes. The results reveal substantial heterogeneity in the benefits of multinational engagement. Firms participating in FDI exhibit higher productivity, capital intensity, and R&D investment than non-FDI firms. However, vertical outward FDI and outward FDI directed toward developed economies generate the strongest productivity gains, while horizontal FDI and investments involving developing economies produce weaker or statistically insignificant effects. These findings suggest that the multinationality–performance relationship depends not only on whether firms internationalize, but also on how they internationalize and where they invest. More broadly, the study highlights the importance of distinguishing among alternative internationalization strategies when evaluating the performance effects of FDI.