Born in Joplin, Missouri, Porter made his debut on September 2, 1971 with the Milwaukee Brewers at age 19. He was selected to the American League All-Star team in 1974, but had his best years after he was traded in 1976 to the Kansas City Royals, where he was selected to the All-Star team four times and in 1979 became only the second catcher in history (after Mickey Cochrane) to have 100 walks, runs, and RBIs in a single season. In addition, he led the league in percentage of baserunners thrown out. He became a fan favorite for his intensity; teammate George Brett once said of Porter, "Darrell always played like it was the seventh game of the World Series."

Porter told the Associated Press that during the winter of 1979-1980, he became paranoid, convinced that baseball commissioner Bowie Kuhn, known to be tough on drug use, knew about his drug abuse, was trying to sneak into his house, and planned to ban him from baseball for life. Porter found himself sitting up at night in the dark watching out the front window, waiting for Kuhn to approach, clutching billiard balls and a shotgun.

During spring training in 1980, former Los Angeles Dodgers pitcher Don Newcombe paid a visit to the Kansas City clubhouse. He asked the players 10 questions, and said if you answered yes to three or more of the questions, you might have a problem with drugs or alcohol. Porter answered yes to all 10 questions and checked himself into a rehabilitation center, admitting he had abused alcohol, cocaine, Quaaludes, and marijuana.

After checking in to the rehab center, Porter became a born-again Christian, married, and became a spokesman for the Fellowship of Christian Athletes; but his production on the field declined, never again approaching his 1979 levels. He went on to play in three World Series, in 1980 with the Royals and in 1982 and 1985 with the St. Louis Cardinals, winning the World Series MVP Award in 1982. After the 1985 season, the Cardinals released him, and he wound up his career with two seasons with the Texas Rangers as a part-time player, ending with a career batting average of .247 with 188 home runs and 826 RBIs in 17 major league seasons.

In 1984, Porter wrote an autobiography titled Snap Me Perfect!, in which he detailed his life in baseball and his struggles with substance abuse.

Porter dabbled in broadcasting late in his life. But, on August 5, 2002, he left home, saying he was going to buy a newspaper and go to the park. He was found dead in Sugar Creek, Missouri outside his vehicle that evening. An autopsy said he had died of "toxic effects of cocaine"; the level of cocaine in his system, consistent with recreational use, induced a condition called excited delirium that caused his heart to stop. He was 50 years old.

Porter was also notable for being one of the few major league catchers of his time to wear eyeglasses behind the plate, at a time when most players needing vision correction were using contact lenses.