linguistic:voice_change, information:classification
 Atlanta Braves (1954–1974)

In 1954, Aaron attended spring training with the major league club. Although he was on the roster of its farm club, Milwaukee manager Charley Grimm later stated, "From the start, he did so well I knew we were going to have to carry him." On March 13, 1954, Milwaukee Braves left fielder Bobby Thomson fractured his ankle while sliding into second base during a spring training game. The next day, Aaron made his first spring training start for the Braves major league team, playing in left field and hitting a home run. This led Aaron to a major league contract, signed on the final day of spring training, and a Braves uniform with the number five. On April 13, he made his major league debut and was hitless in five at-bats against the Cincinnati Redlegs. In the same game, Eddie Mathews hit two home runs, the first of a record 863 home runs the pair would hit as teammates. On April 15, Aaron collected his first major league hit, a double off St. Louis Cardinals pitcher Vic Raschi. Aaron hit his first major league home run on April 23, also off Raschi. In 122 games, Aaron batted.280 with 13 home runs before he suffered a fractured ankle on September 5. He then changed his number to 44, which would turn out to look like a "lucky number" for the slugger. Aaron would hit 44 home runs in four different seasons, and he hit his record-breaking 715th career home run off Dodgers pitcher Al Downing, who coincidentally also wore number 44.

At this point, Aaron was known to family and friends primarily as "Henry". Braves' public relations director Don Davidson, observing Aaron's quiet, reserved nature, began referring to him publicly as "Hank" in order to suggest more accessibility. The nickname quickly gained currency, but "Henry" continued to be cited frequently in the media, both sometimes appearing in the same article, and Aaron would answer to either one. During his rookie year, his other well-known nicknames, "Hammerin' Hank" (by teammates) and "Bad Henry" (by opposing pitchers) are reported to have arisen.

While living in Milwaukee, Aaron resided in the Prinz House in Historic Brewers Hill.

Considerably later in his career, Aaron coined "Stone-fingers", which would prove a popular handle for one of baseball's more colorful characters, the famously distance-hitting but defensively challenged first baseman Dick Stuart, reportedly "delight" even its recipient.

Sal Maglie recommended throwing low curveballs to Aaron. "He's going to swing and he'll go after almost anything," Maglie said of the Braves' slugger. "And he'll hit almost anything, so you have to be careful."