Brooks scored in his Bundesliga debut on August 10, 2013 in Hertha BSC's 6–1 victory against Eintracht Frankfurt. His appearances over the season were limited by injury and poor form, and he also missed time in April 2014 while recovering from the application of a large back tattoo, a decision that did not please manager Jos Luhukay.
In July 2013, German magazine kicker indicated that Brooks had received a call-up from the U.S. senior national team to feature in a friendly against Bosnia and Herzegovina. Brooks made his senior international debut in the 4–3 victory over Bosnia. Brooks was named in the United States's final 23-man roster for the 2014 FIFA World Cup. In the opening group match against Ghana, he came on as a halftime injury substitute for Matt Besler and scored the winning goal in the 2–1 victory, a header off Graham Zusi's corner kick. He became the first American to score as a substitute at the World Cup.