Worden was one of the 19 astronauts selected by NASA in April 1966. He served as a member of the astronaut support crew for the Apollo 9 flight and as backup command module pilot for the Apollo 12 flight.
Worden served as command module pilot for Apollo 15, July 26 - August 7, 1971. His companions on the flight were David Scott, spacecraft commander, and James B. Irwin, lunar module pilot. Apollo 15 was the fourth manned lunar landing mission and the first to visit and explore the moon's Hadley Rille and Apennine Mountains which are located on the southeast edge of the Mare Imbrium (Sea of Rains). Apollo 15 achievements include: Largest payloads placed in earth and lunar orbits; first scientific instrument module bay flown and operated on an Apollo spacecraft; longest lunar surface stay time (the lunar module, "Falcon," remained on ground for 66 hours and 54 minutes); longest lunar surface EVA (Scott and Irwin logged 18 hours and 35 minutes each during three excursions onto the lunar surface); longest distance traversed on lunar surface; first use of lunar roving vehicle; first use of a lunar surface navigation device (mounted on Rover-1); first subsatellite launched in lunar orbit; and first EVA from a command module during transearth coast.
Additionally, Worden has been listed in the Guinness Book of World Records as the "Most isolated human being" during his time alone in the command module "Endeavour". When the orbiting command module was at its greatest distance from Scott and Irwin in the "Falcon", Worden was 2,235 miles away from any other human beings .
Scott and Irwin collected approximately 171 pounds of lunar surface materials on their three expeditions onto the lunar surface; and Worden logged 38 minutes in extravehicular activity outside the command module, "Endeavour." In completing his three excursions to "Endeavour's" scientific instrument module bay, Worden retrieved film cassettes from the panoramic and mapping cameras and reported his personal observations of the general condition of equipment housed there. Apollo 15 concluded with a Pacific splashdown and subsequent recovery by USS Okinawa. In completing his space flight, Worden logged 295 hours and 11 minutes in space.
During 1972-1973, Worden was Senior Aerospace Scientist at the NASA Ames Research Center, and from 1973 to 1975, he was chief of the Systems Study Division at Ames. Between 1972 and 1975, he made seven guest appearances on Mister Roger's Neighborhood.
After retirement from active duty in 1975, Worden became President of Maris Worden Aerospace, Inc., and then became Staff Vice-President of BG Goodrich Aerospace Brecksville, Ohio. Worden is currently the Chairman of the Astronaut Scholarship Foundation, providing scholarships to exceptional science and engineering students.