Miller was moved for goalie Marek Mazanec, a third-round pick in the 2019 draft and a conditional first-round pick in either 2020 or 2021. Tampa Bay used the third-rounder on Swedish goaltender Hugo Alnefelt.
The 26-year-old Miller is signed through 2023 at a $5.25 million cap hit annually. The Lightning had just under $5.9 million in cap space before the deal.
Miller is a versatile player who plays all three forward spots. He scored 13 goals and 34 assists with Tampa Bay last season, his second with the Lightning after being shipped there from the New York Rangers in 2018 in the Ryan McDonagh trade.
The move opens up cap space for the Lightning, who have 17 players under contract for next season. The highest priority is to re-sign standout center Brayden Point this summer. Point, 23, is a restricted free agent coming off a season of 41 goals and 51 assists.