Jagr had 11 goals and 18 assists in 57 games this season for New Jersey. His playing time has been cut recently and he has gone eight games without a point.
Jagr is sixth in NHL history with 716 goals, seventh with 1,068 assists and fifth with 1,784 points in 1,530 career regular-season games in 22 years with Pittsburgh, Washington, the New York Rangers, Philadelphia, Dallas, Boston and New Jersey.
The Czech star also has 78 goals and 121 assists in 202 playoff games. He helped Pittsburgh win Stanley Cup titles in his first two seasons in the NHL in 1990-91 and 1991-92.
Florida was still working out the details Thursday as to when Jagr would make his debut for the team. The Panthers are home against Chicago on Thursday night.
Florida entered Thursday two points out of the final playoff spot in the Eastern Conference.
Jagr, who turned 43 earlier this month, has been in the league longer than the Panthers have. His NHL debut was Oct. 5, 1990; the Panthers played their first game Oct. 6, 1993.
He was part of his native Czech Republic winning gold medals at the 1998 Olympics and the world championships in 2005 and 2010. Jagr owns or shares no fewer than 18 NHL records, including his 127 game-winning goals.
The Panthers scheduled a Thursday evening news conference to announce Jagr's acquisition.