Baltimore Orioles Minor leagues The
Baltimore Orioles drafted Mancini in the eighth round, with the 249th overall selection, of the
2013 Major League Baseball draft. He signed, and made his professional debut with the
Aberdeen IronBirds of the
Low-A New York–Penn League that same year. In 137 games between the two teams, Mancini compiled a .284 batting average with ten home runs and 83 RBI. He began the 2015 season with Frederick, and was promoted during the season to the
Bowie Baysox of the
Double-A Eastern League. In 136 games, Mancini slashed .341/.375/.563 with 21 home runs, 89 RBI, and 43 doubles. After spending some time in Baltimore during
spring training, Mancini returned to Bowie to start the 2016 season. He was blocked at Triple-A by
Joey Terdoslavich, but was nonetheless promoted to the
Norfolk Tides in April as Terdoslavich struggled. He spent the remainder of the season at Norfolk, batting .280 with 13 home runs and 54 RBI in 125 games.
Major leagues The Orioles promoted Mancini to the major leagues for the first time on September 18, 2016, during September call-ups. On September 20, in his major league debut as the
designated hitter against the
Boston Red Sox, he hit a home run against
Eduardo Rodríguez in his second
at-bat. His parents were in attendance to watch this, his first MLB home run. That home run made Mancini the fourth Orioles' player to hit a home run for their first Major League hit after
Larry Haney (1966),
Nick Markakis (2006) and
Jonathan Schoop (2013). Mancini started again two nights later and hit his second career home run, a three-run homer off
David Price. He became the 20th player in major league history to hit a home run in his first two starts. Mancini also became the third player in major league history to homer in their first three starts, after he hit a solo home run against the
Arizona Diamondbacks on September 24. Mancini made the Orioles' 2017
Opening Day roster after transitioning to the outfield. On April 16, 2017, Mancini recorded his second multi-home run game of the season, while driving in four runs. He tied
Trevor Story and
Dino Restelli for most home runs through a player's first 12 career games with seven. On April 22, Mancini hit his fifth home run of the season and eighth of his career. He tied Story and
Carlos Delgado for most home runs through a player's first 17 career games. On June 7, in a game against the
Pittsburgh Pirates, Mancini hit a game-tying, pinch-hit two-run home run in the ninth inning off closer
Tony Watson. Two innings later, with two on and two outs, Mancini hit a walk-off three-run home run off
Wade LeBlanc to give the Orioles a 9–6 victory. Per
STATS, LLC, Mancini became the first Oriole to hit a pinch-hit homer in the 9th inning or later and then hit another home run in the same game. He also became the second Oriole ever to hit a game-tying home run in the 9th inning or later and then hit a walk-off homer in the same game (
Mike Young on May 28, 1987). He also joined
Boog Powell ('66) and
Eddie Murray ('80) as the only three Orioles to homer in the 9th inning and in extras in the same game. Mancini finished the season batting .293/.338/.488 with a .826 OPS, 120 OPS+, 24 home runs and 78 RBI in 147 games during his rookie campaign. He also collected 159 hits on his way to finishing in third place for
American League Rookie of the Year voting. Mancini batted leadoff for 51 of 156 games played in 2018. He ended the season hitting .242 with 24 home runs and 58 RBIs. Mancini was leading the Orioles in most offensive categories in late-April. He is one of three MLB players along with
Alex Bregman and
Anthony Rendon with at least 35 doubles, 34 home runs and 100 runs in 2019. He set a career high with five hits in an 11–4 win over the
Toronto Blue Jays at
Rogers Centre on September 24, 2019. He ended the season hitting .291 with 35 home runs and 97 RBIs. Mancini was awarded the 2019 Louis M. Hatter Most Valuable Oriole Award by members of the local media. On March 7, 2020, Mancini left the Orioles during spring training to undergo a non-baseball medical procedure. On March 12, it was revealed that the procedure was the removal of a
malignant tumor from his
colon. On April 28, Mancini revealed he had stage 3
colon cancer and began
chemotherapy to treat his cancer. On June 28, Mancini was placed on the 60-day
injured list and missed the entire 2020 season due to recovery from Stage 3 colon cancer surgery. He completed chemotherapy in November 2020. In November 2020, Mancini announced that he was cancer-free and planned to play for the Orioles in 2021. He returned to the Orioles at the beginning of spring training and appeared in the team's first game of the preseason, against the
Pittsburgh Pirates. Mancini was given a standing ovation by the Orioles crowd prior to his first at-bat of the season in Baltimore. He finished the 2021 season batting .255/.326/.432 with 21 home runs and 71 RBIs in 147 games. On November 22, 2021, Mancini was awarded the
American League Comeback Player of the Year Award. On July 28, 2022, Mancini hit an
inside-the-park home run with a runner on base that started as what appeared to be a routine
sacrifice fly. However, the ball deflected off the cheek of
Tampa Bay Rays right fielder
Josh Lowe after he lost it in the afternoon sun, allowing Mancini to score. It was a very memorable at-bat for Orioles fans for two reasons: 1. Due to the park’s commemoration of
Mo Gaba,
Baltimore’s number one sports fan who passed on the same day in 2020, and 2. It ended up being Mancini's final at bat as an Oriole at
Camden Yards.
Houston Astros The Orioles traded Mancini to the
Houston Astros in a three-team trade on August 1, 2022, in which the Orioles acquired
Seth Johnson from the
Tampa Bay Rays and
Chayce McDermott from Houston, the Rays acquired
Jose Siri from Houston, and the Astros also acquired
Jayden Murray from the Rays. Mancini hit a home run for his first hit as an Astro on August 3 to help lead a 6–1 win against the
Boston Red Sox. On August 5, Mancini hit his first career
grand slam against
Hunter Gaddis of the
Cleveland Guardians as part of a two-homer, 5 RBI day. He homered on August 18 on the way to a 21–5 win over the
Chicago White Sox that included 25 hits, tied for both the second-highest scoring output and most hits in team history. The Astros defeated the Rays 4–0 on September 19 to clinch the
AL West division title, which made Mancini a division title winner for the first time in his career. In 2022 between the two teams, Mancini batted .239/.319/.391 in 519 at-bats, with 18 home runs and 63 RBI. He split time between 71 games at
DH, 39 at first base, 20 in left field, and 11 in right field. The Astros declined Mancini's option for 2023, thereby making him a free agent.
Chicago Cubs On January 20, 2023, Mancini signed a two-year, $14 million contract with the
Chicago Cubs. Before the signing, he had agreed to play for the
Italy national baseball team in the
2023 World Baseball Classic. However, after signing, he withdrew from the WBC. Mancini batted .234 with 4 home runs and 28 RBI in 79 games for the Cubs before he was
designated for assignment on August 1. He was officially released by the Cubs the next day.
Cincinnati Reds On August 23, 2023, Mancini signed a minor league contract with the
Cincinnati Reds organization. Mancini hit .316 with two home runs in five games with the Triple–A
Louisville Bats before he was released on August 30.
Miami Marlins On January 24, 2024, Mancini signed a minor league contract with the
Miami Marlins organization. On March 23, he opted out of his contract and became a free agent.
Arizona Diamondbacks On February 7, 2025, Mancini signed a minor league contract with the
Arizona Diamondbacks. In 74 appearances for the Triple-A
Reno Aces, he batted .308/.373/.522 with 16 home runs, 62 RBI, and two stolen bases. Mancini triggered the opt-out clause in his contract and was released by the Diamondbacks on July 1.
Los Angeles Angels On January 26, 2026, Mancini signed a minor league contract with the
Los Angeles Angels. ==Personal life==