Chelsea will sign Germany international Andre Schurrle from Bayer Levekusen, after the two clubs reached an agreement.
Schurrle has long been a target for the Blues and becomes the first transfer since the appointment of new manager Jose Mourinho in what is reported to be an £18million deal.
It had been expected Chelsea midfielder Kevin de Bruyne would move on loan as part of the deal, following a successful spell in the Bundesliga at Werder Bremen last season.
However, Chelsea's statement this afternoon made no mention of the 21-year-old, with Mourinho suggesting at Monday's press conference the player was very much in his first-team plans as the new Blues boss aims to bring through the next generation, like Romelu Lukaku, alongside established first-team players such as club captain John Terry and England midfielder Frank Lampard.
A statement on the club website, www.chelseafc.com, read: "Chelsea Football Club and Bayer 04 Leverkusen have reached an agreement for the transfer of Andre Schurrle, subject to the completion of legal documentation and related matters, including personal terms and passing a medical."
Mourinho, who agreed a four-year deal to return to Stamford Bridge following his departure from Real Madrid, admitted it was "normal" to expect some fresh faces to be added to the squad.
Chelsea have been heavily linked with Napoli's £30million-rated frontman Edinson Cavani, who is said to also be on the radar for Manchester City and Madrid, as well as Wayne Rooney, should the England striker be sold by Manchester United.
However, the new Blues manager, who won the Champions League for a second time with Inter Milan after leaving Stamford Bridge six years ago, maintained he was also looking to bring on the club's younger players in the new campaign.
Chelsea finished third last season under interim-manager Rafael Benitez, who also overcame initial difficulties to guide the team to success in the Europa League.
Mourinho, though, has made it clear he views success as improvement in their Barclays Premier League title challenge and progress through to the latter stages of the Champions League.
Speaking earlier this week, Mourinho said: "These 'kids' - and I say that respectfully - have big potential and big space for improvement. They have not reached their best level," he said.
"The stability the owner and I can give them is related to work - in the methods, the coaching philosophy, in my leadership, in everything that can help them improve.
"When you mix with them those who are over 30, we will keep a balance and try to go on."
As usual during any transfer window, Chelsea have been linked with a string of players.
Vitesse Arnhem midfielder Marco van Ginkel, 20, is one reported target, as is senior Dutch international Wesley Sneijder, currently with Galatasaray.
Bayer Leverkusen, meanwhile, have been quick to bolster their attacking options with the acquisition of South Korean forward Heung-Min Son from Bundesliga rivals Hamburg.