Starting the US Series, del Potro won the 2013 Citi Open in Washington DC, where he got a first-round bye, and then defeated Ryan Harrison, Bernard Tomic, and Kevin Anderson on his way to the quarterfinals, Tommy Haas in the semifinals, and won the final against John Isner in three sets. Before the final he didn't drop a set. This was his third title at the event and his second of the year. Del Potro reached the semifinals of Western & Southern Open where he won against Nikolay Davydenko, Feliciano López, in the quarterfinals Dmitry Tursunov, and faced Isner again, this time in the semifinals. He lost the match in three sets. Del Potro got to the second round of the US Open, after a four-set victory against Guillermo García-López, only to be upset by Lleyton Hewitt in five sets.