The 35-year-old has enjoyed a glittering career at Stamford Bridge, collecting 11 major honors - including three Premier League titles and one Champions League - but announced Monday that he will leave.
Lampard became the club's record goalscorer with a double in a 2-1 victory over Aston Villa in May 2013 and will leave having netted 211 goals to his name from 648 appearances but was limited to 20 Premier League starts under Jose Mourinho this season and found his place even harder to nail down after Nemanja Matic's January return to the club.
"It was very difficult," the midfielder told reporters of his decision in the build-up to England's pre-World Cup friendly against Ecuador. "After 13 years, the club was part of my life. It is difficult, but you have to move on, the club will move on. I'll probably address it more to the Chelsea fans at a better time.
"I am here to concentrate on England. It was almost a relief to say it so I can move forward. I am really happy to be among an exciting England squad, full of skill, speed and exuberance."