Terms of the deal were not disclosed but local media said the Czech Republic forward, who has not played in the NHL since the 2007-2008 season, agreed to a one-year contract for $3.3 million.
The busy Flyers also announced they had signed free agent center Max Talbot from the Pittsburgh Penguins in what local media said was a five-year deal worth $9 million.
The signings marked yet two more major offseason moves by a Flyers team that signed free agent goalie Ilya Bryzgalov and traded away captain Mike Richards and high-scoring center Jeff Carter last week.
Jagr, 39 and a former NHL most valuable player, helped the Penguins win two Stanley Cups during his 11 years with the team. He has scored 646 goals and accrued 1,599 points in 1,273 career NHL games.
He has spent the last three seasons playing in Russia's Kontinental Hockey League.
Earlier Friday, the Penguins said they withdrew their one-year, $2 million offer to Jagr to avoid getting into a bidding war, followed by the Detroit Red Wings.
Talbot, 27, helped Pittsburgh to the 2009 Stanley Cup championship, scoring both goals in the Penguins's 2-1 win over Detroit in Game Seven. He had eight goals and 13 assists for Pittsburgh last season.
Meanwhile, the Red Wings have agreed to terms with Swedish defenseman Jonathan Ericsson and wings Patrick Eaves and Drew Miller, keeping all three players in Detroit.
The team also signed veteran defenseman Mike Commodore on Friday, the first day of NHL free agency. The 31-year-old Commodore played for the Columbus Blue Jackets last season.
Ericsson agreed to a three-year, $9.75 million deal, and Eaves was brought back for three years and $3.6 million.
Miller reached a two-year agreement for $1.65 million.
Ericsson has played four seasons in the NHL, all with Detroit. He set career highs in 2010-11 in games (74), points (15) and penalty minutes (87).
"Jonathan Ericsson has made significant strides with us over the last three years," general manager Ken Holland said. "We believe in his abilities, we like the physical dimension that he brings to our team and we look for his continued progression as a player over the next few seasons as he enters into the prime of his career." Eaves is coming off a season in which he had 13 goals and seven assists in 63 games for the Red Wings.
"All three guys are 27 years of age," Holland said of the three returning players. "All three of them, I think, their best years are ahead of them." Commodore, who signed a one-year deal, joins his sixth NHL team. He played 20 games for Columbus last season. He asked for a trade and was waived, but at the time, his contract made it hard for other teams to pick him up.
Detroit lost in the second round of the playoffs to San Jose, but got good news recently when Nicklas Lidstrom decided to return.
