The 20-year-old put pen to paper on his deal with the west London club on Saturday afternoon, less than 24 hours after Chelsea announced the arrival of striker Alexandre Pato on loan from Corinthians.
Miazga joined the Red Bulls Academy in 2009 and signed his first professional contract four years later at the age of 17.
The centre-half made his debut for the US national team in November having represented his country at Under-20 and Under-23 level.
Chelsea shared the picture above of Miazga signing his contract on the club’s official Instagram account and wrote: “Welcome to Chelsea, Matt Miazga! #CFC #Chelsea.”
It remains to be seen whether Miazga could be involved when Chelsea travel to MK Dons in the fifth round of the FA Cup on Sunday afternoon.
Defending champions Chelsea are currently in 13th place in the Premier League table.
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