On March 27, 2017, Lettieri signed a two-year entry-level contract as a free agent with the New York Rangers of the National Hockey League (NHL).[2] He was invited to the Rangers training camp before the 2017–18 season but was cut and sent to the Hartford Wolf Pack before the final roster was made.[3] On December 29, 2017, Lettieri made his NHL debut in a 3–2 loss to the Detroit Red Wings, in which he scored his first NHL goal.[4] He was recalled multiple times in January and February before finally being assigned back to the AHL on February 26 after playing in a total of 19 NHL games that season.[5]
Lettieri spent the 2018–19 season rotating between the NHL and AHL getting called up for longer stints in the second half of the season. He finished the season with one goal and two assists. His lone goal came on a one-timer shot on March 25, 2019, against the Pittsburgh Penguins for his first career goal at Madison Square Garden.[6]
Anaheim Ducks
After four seasons within the Rangers organization, Lettieri left as a free agent and signed a one-year, two-way contract with the Anaheim Ducks on October 10, 2020.[7] On July 13, 2021, Lettieri was signed to a one-year, two-way contract extension by the Ducks.[8]
Boston Bruins
On July 13, 2022, Lettieri was signed to a one-year, two-way contract by the Boston Bruins.[9]
After impressive play for the Bruins AHL affiliate the Providence Bruins, Lettieri was named an AHL All-Star, representing the Atlantic Division.[10] Later, Lettieri was called up to the NHL squad on January 26, 2023. However, he suffered an injury just one day later, causing him to be placed on IR.[11] Once healed, Lettieri was then placed on waivers without having played a game for the Bruins, where he cleared.[12] Towards the end of the 2022-23 season, with the Bruins comfortable in the standings, Lettieri was once again called up in order to rest key players. He played one game for the NHL squad before being sent back down.[13]
Minnesota Wild
As a free agent from the Bruins, Lettieri returned to his home state in agreeing to a two-year, two-way contract with the Minnesota Wild on July 1, 2023.[14]
Lettieri did not make the Wild's opening night roster to start the 2023-24 season, but he was called up shortly thereafter on October 23, 2023, and would play his first game in a Wild uniform the next night. Lettieri would score his first goal and point as a member of the Wild on November 7, 2023, in a 4-2 win over the New York Islanders. It was also his first goal at the NHL level since January 26, 2022, when he was still a member of the Ducks. Lettieri notched another goal and an assist before being sent back down to the AHL. After four games in the minors in which he score four points, Lettieri would be called back up to the NHL, where he would spend the rest of the season. Lettieri would score a goal in his first game back with Minnesota. For the rest of the season, Lettieri would serve as a depth forward for a mediocre Wild team. After a brief stint on the IL for almost all of January, Lettieri would be serviceable to the Wild, not providing wowing offense but also not being a liability. He would finish the season with five goals and four assists in 46 games.
Second Stint with the Bruins
On June 29, 2024, on the second day of the 2024 NHL entry draft, Lettieri was traded back to the Bruins alongside the 110th pick in the draft for Jakub Lauko and the 122th pick.[15]
