HOUSTON, Dec. 28— Jimmy Demaret, the first golfer to win the Masters tournament three times and a member of the Professional Golfers Association and World Golf halls of fame, died here today, apparently of a heart attack. He was 73 years old.

Laura Guillot, an official with Champions Golf Club, of which Mr. Demaret was co-owner, said that he had reported to work when he suffered the attack. Pat Morgan, his business associate and close friend, said that Mr. Demaret had collapsed while getting into a golf cart to drive around the course, which he designed and built with another former professional golfer, Jack Burke Jr.

Mr. Demaret won the Masters in 1940, 1947 and 1950, but he never won the United States Open, P.G.A. or British Open. He was the leading money winner on the PGA Tour in 1947 with $27,936 and achieved 31 career victories on the tour. Won 9 Events in 1940

Mr. Demaret won nine tournaments on tour in 1940 and seven in 1947. He also won the Vardon Trophy in 1947, which is awarded to the tour member with the year's lowest stroke average per round. His first tournament victory was in 1934, the Texas P.G.A., where he earned $25.

Mr. Demaret played on three Ryder Cup teams against British teams and was unbeaten in six matches. He was named to the P.G.A. Hall of Fame in 1960. When he was inducted into the World Golf Hall of Fame last May, he wore a bright apricot sweater with white knickers, argyle socks and orange and black golf shoes.

Mr. Demaret often chose bright clothes during a period when everyone wore whites. His clothes were made to order - electric blue, bottle green, canary yellow and vermilion were among his favorites. His hats were considered outlandish; a Swiss yodeler's hat was a staple for a while.

His first major victory came in 1938, when he beat Sam Snead for the National match-play title in San Francisco. After he left the tour, he devoted the majority of his time to the operation of the Champions Golf Club. Joined Tour in 1938

Mr. Demaret was born May 24, 1910, in Houston, the fourth of nine children born to a house painter-carpenter. He got his first job as a club pro in 1932 in Galveston, Tex., before joining the tour in 1938.

After his retirement as an active player, he worked as a television commentator and was the host of the ''Wonderful World of Golf'' television series during the 1960's.

Bill Bass, general chairman of the Legends of Golf tournament in Austin, Tex., an event for players 50 and older, called Mr. Demaret ''a fine, fine friend of ours.'' He said Mr. Demaret was one of the owners of Onion Creek Club, where the Legends is played, and had designed the course.

One of those legends, 71-year-old Mr. Snead, said from his home in Hot Springs, Ark.: ''He was a happy-go- lucky person, he liked to party at night and he never liked to sleep more than a few hours. No telling what Jimmy would have done if he'd toed the line and gone to bed at a decent hour.''

''It's amazing how much he meant to golf,'' said Ben Crenshaw, a fellow Texan who is active on the professional tour and a student of the game's history.

Mr. Demaret is survived by his wife, Idella, and a daughter, Peggy Jackson of Houston. The funeral will be private.

James Demaret (1910)