Langkow rejoined the Lightning for the 1996–97 NHL season and scored 15 goals and 28 points in his rookie season. He scored his first NHL goal on November 19, 1996, against the Los Angeles Kings, and was named the NHL's rookie of the month for February 1997. He fell to 22 points in 1997–98 and ended the season in a dispute with the Lightning when he refused a demotion to the Adirondack Red Wings of the American Hockey League. The Lightning suspended him indefinitely, but told the media they were not interested in trading him. He missed seven games and lost $63,000 in salary before the Lightning relented and recalled him to finish the season in Tampa. Langkow was assigned to the Cleveland Lumberjacks of the International Hockey League to begin the 1998–99 season amidst trade rumours but was recalled after four games. He was traded to the Philadelphia Flyers along with Mikael Renberg on December 12, 1998, in exchange for Chris Gratton and Mike Sillinger.