The London-based International Tennis Integrity Agency (ITIA) announced the punishments Tuesday, saying that Fish and Bryan cooperated fully with its investigation and removed the problematic posts immediately.
The bans will be enforced only if there is another breach by Fish or Bryan during the four-month probationary period that began on Nov. 11.
"Bob and I did a DraftKings promo during the US Open that we were unaware we weren't allowed to do," Fish wrote in an email to The Associated Press on Tuesday. "As soon as we found out, I deleted the posts and cooperated with the ITIA."
Fish, the U.S. Davis Cup captain since 2019, and Bryan, who has been a coach and served as an acting captain this year when Fish was sidelined with COVID-19, were "subject to the sport's rules around relationships with betting operators," the ITIA said.
The United States reached the Davis Cup quarterfinals this season, losing to Italy at that stage in Malaga, Spain, last week. The Americans have won a record 32 titles in the international team competition for men, most recently in 2007.
The sport's anti-corruption program says anyone who falls under its jurisdiction -- which Fish and Bryan did as people accredited for the U.S. team in 2022 -- is not allowed to "directly or indirectly facilitate, encourage and/or promote" betting on tennis.
"The USTA is aware of the ITIA's fines of Mardy Fish and Bob Bryan. Both Mardy and Bob have our full support. As was stated by the ITIA, neither was aware that their actions were in any way a violation of protocols, and when they were made aware immediately and fully cooperated with the ITIA throughout the remainder of the process," a spokesman for the U.S. Tennis Association said in an emailed statement. "Mardy and Bob have given so much of their lives to representing and supporting U.S. tennis and we are thankful for their ongoing commitment to growing the game throughout the country."