This paper examines the impact of Uber, the world’s largest ride-hailing firm, on congestion. Drawing on data from large urban areas in Europe and the United States for the period 2008 through 2016, it finds a negative impact of Uber on congestion in Europe and a positive impact in the United States. Results suggest that ride-hailing firms have brought about an increase in vehicle utilization of for-hire cars with drivers in Europe, while they have promoted an increase in the size of the for-hire car with drivers sector in the United States.