McBean grew up playing baseball in his native Virgin Islands. He was discovered when the Pittsburgh Pirates held a tryout in St. Thomas in 1957. Originally only there to take pictures for a local paper, McBean was convinced by friends to tryout, and ended up receiving an invite to Spring training 1958.
After three seasons in the Pirates' farm system, in which he went 28-21 with a 3.57 earned run average, McBean made his major league debut on July 2, 1961 in the first game of a doubleheader against the San Francisco Giants at Forbes Field. Entered a tied game, the first batter he faced, Ed Bailey, reached on an error by second baseman Bill Mazeroski. A double, wild pitch & single later, the Giants had plated two runs. A four run eighth inning by the Pirates spared McBean from taking the loss in his major league debut.
McBean was flawless in his next six appearances, pitching 10.2 innings without surrendering a run, and earning the first two wins of his career. His first career start also came against the Giants on September 11. He allowed three earned runs over nine innings, and left with the game tied for the no-decision. For the season, he went 3-2 with a 3.75 ERA & 49 strikeouts.
McBean was converted into a full time starting pitcher in 1962, and won his first three decisions. He emerged as the Pirates' second most consistent pitcher (behind Bob Friend) with a 15-10 record & 3.70 ERA over the full season.
He was 2-1 with a 3.46 ERA when he was converted into a reliever in May 1963. He was dominant in that role, going 11-2 with a 2.12 ERA and earning eleven saves out of the bullpen. After the season, he joined Roberto Clemente's National League Latino All-stars for a game at the Polo Grounds on October 12. McBean followed Juan Marichal's four scoreless innings pitched with four scoreless of his own, and drove in a run with a sixth inning triple to lead the NL to a 5-2 victory.
McBean was even more dominant in 1964. Following a June 27 victory over the Cincinnati Reds, McBean was 3-0 with an 0.69 ERA & eight saves. He earned 21 saves over the season, which was good enough for second place in the NL (to the Houston Colt .45s' Hal Woodeshick). Coupled with his 8-3 record, he was named The Sporting News' NL Fireman of the Year. He was again one of the NL's top relievers in 1965, going 6-6 with a 2.29 ERA & 19 saves.
With Roy Face returning in 1966 from an injury plagued 1965 season, he resumed the closer role. Meanwhile, manager Harry Walker relegated McBean to mop up duty. He appeared in 32 of the Pirates' 70 losses; the Pirates were 15-32 in games he appeared.
Walker was fired midway through the 1967 season, and replaced by his predecessor, Danny Murtaugh. At the time, McBean was 2-1 with a 3.04 ERA & four saves. After sixteen appearances out of the bullpen for Murtaugh, McBean was returned to the starting rotation. He went 4-1 with a 2.11 ERA & five complete games in seven starts for the manager he broke into the big leagues with. He went 9-12 with a 3.58 ERA in 1968.
McBean was the fiftieth player selected in the 1968 Major League Baseball expansion draft by the San Diego Padres. He made just one appearance with the Padres before being dealt to the Los Angeles Dodgers for shortstop Tommy Dean & pitcher Leon Everitt. Again a reliever, McBean went 2-6 with a 3.91 ERA & four saves out of the Dodgers' bullpen. After just one inning pitched with the Dodgers in 1970, McBean was released, and he returned to Pittsburgh. He would make seven appearances, all in relief, before his May 18 release. He would pitch in the Philadelphia Phillies' system into the 1971 season before retiring.
McBean was a decent hitting pitcher. He had three career home runs, one of which came in his second career at bat. He also hit a grand slam off the St. Louis Cardinals' Larry Jaster.List of Major League Baseball all-time saves leaders
On August 27, 1962, McBean married Olga Santos. Roberto Clemente was his best man. Upon retirement, McBean returned to the Virgin Islands, and joined the St. Thomas Housing, Parks & Recreation Department. Moving up to deputy commissioner, he chartered the Little League program & beautification projects. He also has a landscaping business. He also opened the Alvin McBean Recreation Complex on St. Thomas.