The first Dominican to play regularly in the major leagues, he is the most prominent member of one of the sport's most notable families of the late 20th century: he was the oldest of the trio of baseball-playing brothers that included Matty and Jesús, who were both primarily outfielders, and his son Moisés was also primarily an outfielder; all but Jesús have been named All-Stars at least twice.

[a] During his 17-year career spent with the Giants, Milwaukee / Atlanta Braves, Oakland Athletics, New York Yankees, Montreal Expos, and Milwaukee Brewers, Alou played all three outfield positions regularly (736 games in right field, 483 in center, 433 in left), and led the National League twice in hits and once in runs.

Batting regularly in the leadoff spot, he hit a home run to begin a game on 20 occasions.

[2] He is one of just three men to have 2,000 hits, 200 home runs, and 1,000 managerial wins (the other two are Joe Torre and Frank Robinson).

He played baseball in college team while getting ready for the 1955 Pan American Games (held in March), aiming for track.

He planned to stay with his studies, but he attracted interest in baseball due to his university coach, who had served as a scout with the Giants.

All three formed the first and only all-brother outfield in MLB history in the last two innings of a 13–5 win over the Pittsburgh Pirates at Forbes Field on September 15, 1963.

"[13][14][15] Despite playing with a handful of Latino players (such as Orlando Cepeda) on the Giants, manager Alvin Dark did not allow them to speak Spanish in the clubhouse, which displeased Alou, who noted it decades later in his memoirs; the two became friends after Alou retired because of their shared Christian faith.

While the Braves went to the 1969 National League Championship Series after winning the NL West, Alou appeared just once, doing so as a pinch hitter in Game 3.

Facing Nolan Ryan, he lined out in the eighth inning for his last postseason appearance as a player.

After the end of his playing career, Alou joined the Montreal Expos organization in 1976, becoming a batting coach and a minor league manager.

[25] The team was developing a core of young talent during this period, including Larry Walker, John Wetteland, Delino DeShields and Alou's own son, Moisés.

In 1994 the Expos had the best record in the major leagues until the mid-August strike that ended up cancelling the entire postseason, thereby denying them a chance to get to their first World Series, and ownership soon began dealing all their young talent to cut payroll.

The Los Angeles Dodgers tried to lure him away in 1998, but he declined to leave Montreal and eventually became the most successful manager in team history.

Despite Alou's popularity in Montreal, the Expos' lackluster record after 1994 eventually led to his dismissal by new owner Jeffrey Loria, who replaced him with Jeff Torborg during the 2001 season.

He finally agreed to serve a single year as the bench coach for Detroit Tigers rookie manager Luis Pujols (2002).