Foreign direct investment (FDI) occurs when an entity in one country establishes a significant degree of ownership in an enterprise in another country. FDI is a critical component in ensuring the development of any economy. It often aids with the development of an industry or sector within an economy by bringing in capital, new technologies, manufacturing methodologies, and managing expertise to the receiving country. This dissertation examines the relationship between policy uncertainty and foreign direct investment (FDI) in developed economies. The first essay focuses on U.S. policy uncertainty and its effects on U.S. FDI inflows, while the second essay focuses on the cross-border effect of U.S. policy uncertainty on its neighbours FDI inflows. The third essay focuses on how policy uncertainty affects the investment entry mode choices of multinational enterprises. In the first essay, I add to the discussion surrounding Foreign Direct Investment (FDI) and its relationship with policy uncertainty by employing novel measures of policy uncertainty in the United States. Drawing some conclusions from the Real Options investment theory, I examine the relationship between policy uncertainty and FDI inflows using different measures of policy uncertainty. Overall, I find that an increase in the Partisan Conflict (PC) index increases the flow of FDI into the United States. This finding appears at odds with what has previously been found in the literature regarding political uncertainty and FDI. Using other measures of policy uncertainty such as the Economic Policy Uncertainty index (EPU) and the categorical EPU (CPU) index the estimated results show policy uncertainty as measured by the EPU index, decreases FDI into manufacturing sectors and decreases FDI into non-manufacturing sectors. This effect varies depending on the sample period being examined. However, when policy uncertainty is measured by the CPU index, policy uncertainty has no impact on FDI inflows to the United States regardless of the type of industry or capital intensity. The second essay examines how U.S. policy uncertainty spillovers affect its neighbours within the context of FDI inflows. Adopting a common framework employed in the literature, I utilize a Vector Autoregressive (VAR) model to examine the contemporaneous relationships between the endogenous and exogenous variables. The two spillover transmission methods examined in this paper are Direct Transmission and Indirect Transmission. The empirical analysis conducted showed that the significance of U.S. policy uncertainty spillovers varied by country and the method of transmission. Canadian FDI inflows from the United States and from the rest of the world were shown to be more susceptible to the negative effects of U.S. policy uncertainty spillovers via the direct channel. But the results remained mixed when considering the indirect channel. For Mexico, the results showed that only U.S. FDI inflows to Mexico were susceptible to the negative effects of U.S. policy uncertainty via the indirect channel. Furthermore, when policy uncertainty spillovers were defined between Partisan Conflict (PC) index and the Economic Policy Uncertainty (EPU) index, the results showed that only EPU spillovers were significant in affecting FDI across Canada and Mexico. The third essay examines the mode of entry that Japanese multinational enterprises (MNEs) adopt in the presence of host market policy uncertainty. Employing a two-stage framework, I examine how Japanese MNEs establish foreign affiliates in 25 countries. In the first stage, the firms decide whether to adopt a direct or an indirect mode of entry in the presence of host market policy uncertainty. A direct entry mode is when the MNE has an ownership share in the affiliate that is greater than 10% while an indirect entry mode is when the MNE has no ownership shares in the affiliate but sets the operational and business goals of the affiliate. The results show that Japanese MNEs preferred an indirect mode of entry when faced with medium levels of policy uncertainty. In the second stage the estimated results show that relatively high levels of policy uncertainty caused Japanese MNEs to prefer minority Joint Ventures over establishing Wholly Owned Subsidiaries. Since 58% of observed investments occur in two countries (China, the United States) it is possible that the results of the analysis are being driven by the concentration of investments in both countries. Therefore, I re-examine the model to focus exclusively on investment activities in China and the United States. These results show that the previously described results were due to the investment activity in these two countries.