"As an athlete, I can think of no greater honor than representing the United States in the Olympic Games. However, after much careful consideration and discussion with both my family and my team, I have made the decision to withdraw from the 2016 Olympic Games," Johnson wrote in a statement.
The world's second-ranked golfer said he and his wife Paulina, the daughter of hockey legend Wayne Gretzky, plan to have more children in the future and thought it would be "irresponsible" to put his family at risk of the virus.
Johnson joins top-ranked Jason Day of Australia, fourth-ranked Rory McIlroy of Northern Ireland and eighth-ranked Adam Scott of Australia, among others, as notable players who have opted to skip Rio because of Zika fears.
Johnson won his first major on June 20, claiming a three-shot victory at the 116th U.S. Open at historic Oakmont Country Club in Oakmont, Pa.
The 32-year-old American followed with a one-shot win in last weekend's World Golf Championship-Bridgestone Invitational at Firestone Country Club (South Course) in Akron, Ohio.
Johnson ranks first in the FedExCup standings with 2,411 points.