The 20-year-old was born in London but played for Ireland – the country of his grandparents – from the Under-16 side upwards, making three senior appearances in friendly matches.
However, Rice confirmed last month that he intends to represent England in future, announcing his decision after deliberating for some months, consulting England boss Gareth Southgate, former Ireland manager Martin O'Neill and his successor Mick McCarthy in the process.
The switch has now been ratified, which means Rice can be called up by Southgate for England's games against the Czech Republic and Montenegro. The squad will be announced on March 13.
"FIFA can now confirm that the change of association of Declan Rice from Republic of Ireland to England has been approved," a FIFA spokesperson confirmed to Omnisport.
The midfielder has earned rave reviews this season, cementing his place in the West Ham team and winning the Young Player of the Year Award at the London Football Awards last month.
He said of his international future after collecting that prize: "I played three games for Ireland at international level. I made the switch to England, nothing's guaranteed because there are some unbelievable players in the England set-up.
"I've got to be hopeful the paperwork goes through as well. I believe it's with FIFA at the moment, so I'm just hoping that gets through in time, and in the matches between now and the March call-ups I can do enough to maybe get in the squad."
Rice has now been given that green light and is being tipped to make Southgate's next selection, with his performances in the Premier League putting him firmly in the frame.