investigate the global spillover effects of US monetary policy uncertainty in these three essays. In the first chapter, I focus on the impact of uncertainty on the macroeconomic activity of other advanced and emerging economies. I find that an increase in US monetary policy uncertainty reduces output, investment, consumption, exports, and imports in these economies. Such adverse effects are larger in relatively open than closed economies in trade and capital flows. Central banks around the world respond to heightened uncertainty by cutting policy rates, which is further validated by the evidence from central bank minutes. In the second chapter, I examine asset price spillovers from US monetary policy uncertainty to global asset prices. An increase in US monetary policy uncertainty raises sovereign yields and depreciates exchange rates in advanced and emerging economies. A higher level of uncertainty weakens the global transmission of US monetary policy to asset prices. Spillovers from uncertainty to asset prices are larger for the countries with high trade integration, but such effects on sovereign yields are larger only in advanced economies with higher financial integration and the exchange rate peg than the flexible regime. The third chapter investigates how uncertainty about US monetary policy affects cross-border bank flows. I find that an increase in US monetary policy uncertainty reduces cross-border bank lending. In response to higher uncertainty, banks reallocate their portfolio from foreign to domestic borrowers. Such cross-border effects are found to be higher in countries with low capital controls.