Chelsea have brought defender Mamadou Sarr back from Strasbourg, while fellow centre-back Aaron Anselmino has moved to the French club instead. Both players are 20 years old.
The deal is another transfer between Chelsea and Strasbourg, who are owned by the same group, BlueCo. It is the 12th deal between the two clubs this season.
Strasbourg have also signed Chelsea striker David Datro Fofana on loan until the end of the campaign after their main forward, Emmanuel Emegha, picked up an injury in training.
Sarr is not expected to arrive in London until Tuesday, meaning he is unlikely to play in Chelsea’s Carabao Cup semi-final second leg against Arsenal on the same day.
The moves come during a busy and complicated end to Chelsea’s transfer window. The club failed in an attempt to sign Rennes defender Jeremy Jacquet, who instead joined Liverpool in a deal worth up to £60m.
Meanwhile, Anselmino had only just returned from a loan spell at Borussia Dortmund, where his sudden recall reportedly upset the German club. Dortmund officials said they were unhappy with how the situation was handled after Chelsea recalled him shortly before a recall deadline.
