The former world number one has been focusing on doubles involvement since making a return to playing following surgery on his hip in January. He won his first tournament back at Queen's in June, but suffered early knock-outs at both Eastbourne and Wimbledon.
Murray teamed up with Serena Williams in the mixed doubles at SW19 but ruled out a return to singles action during the American hard court season, admitting he was unsure if he would carry on with doubles or attempt to make a return to singles.
In a video posted to Twitter, the 32-year-old revealed his plans for Washington, adding: "I am going to be competing in Washington next week in the doubles with my brother Jamie.
"I am very excited to be on the court with him and go back to Washington, it is a city I have always enjoyed visiting.
"It should be fun and I am hoping to have a good summer over in the states, keep progressing physically and hopefully get on the singles court soon.''
Jamie Murray is the reigning mens doubles champion at Washington, having defeated Mike Bryan and Edouard Roger-Vasselin in the 2018 final with partner Bruno Soares.
The Murray brothers last teamed up at the Rio Olympics, and formed a formidable partnership during Great Britain's 2015 Davis Cup success. They also have two ATP Tour titles to their name from Valencia in 2010 and Tokyo in 2011.
Andy Murray came in for criticism from Washington tournament chief Keely O'Brien after pulling out of last year's event.
In the process of making a comeback from a first operation on his troublesome hip, Murray broke down after winning a gruelling battle with Marius Copil that ended at 3am local time, and said afterwards he didn't know whether he would be able to play his next match.
He eventually withdrew from the tournament, with O'Brien telling the Washington Post: "I hope that Andy really takes into consideration this role in his sport, and as a global role model to guys and girls on the tour and kids around the world that, when things are difficult and tough and the conditions aren't great, it's not okay to just give up."
Mark Ein, chairman of MDE Tennis who took over management rights for the tournament earlier this year, said: "We set out to make doubles a highlight of the Citi Open and the entry list has exceeded even our highest expectations.
“With virtually all of the best players in the world and some incredibly intriguing pairings, we think doubles will be one of the most compelling, entertaining and popular parts of the 2019 Citi Open for our fans.”
Also appearing in the doubles competition are world number six Stefanos Tsitsipas of Greece and Australia's Nick Kyrgios, who are pairing up for the first time. The duo have never faced each other on the singles circuit. Soares is also back this year, and will compete with partner Mate Pavic of Croatia.
The 2019 Wimbledon Mens Doubles champions, Juan Sebastian Cabal and Robert Farah, are also taking part in Washington and are the top seeds ahead of Friday's draw.
The Citi Open starts on July 27, lasting until August 4.