Nottingham Forest have confirmed on their website that they have secured the 18-year-old on a four-month loan deal and revealed Chalobah will be available to play in his new side's trip to Doncaster Rovers on Saturday.
Chalobah completed the official details of the loan deal on Thursday.
"What a long day," Chalobah tweeted.
"Finally at the hotel and pleased to have signed for @Official_NFFC until Jan.
"Looking forward to the challenge."
Chalobah has yet to make a senior appearance for Chelsea after spending last season on loan with Watford in the Championship and was critical to the London club's run to the play-offs, where they lost the final in extra-time to Crystal Palace to just miss out on a spot in the English Premier League.
The Sierra Leone-born teenager played 42 games for Watford last season, regularly anchoring Gianfranco Zola's midfield and has been sent to Forest to earn further experience.
Chelsea manager Jose Mourinho does not believe Chalobah is ready to break into his first team yet, especially with the reigning Europa League champions having such riches in midfield, including Eden Hazard, Oscar, Frank Lampard and Juan Mata.
Chalobah has represented England at Under 16, U17, U19 and U21 level and won the English FA Youth Player of the Year award in February.
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