Steve Carell will depart his role as Dunder Mifflin boss Michael Scott at the end of the latest run of the NBC series. Arnett is one of a number of actors tipped to replace him on the comedy show and his cameo slot has fuelled rumours that he may become a full-time cast member.
Gervais, the creator and star of the original UK series, personally recommended the Arrested Development actor earlier this year.
NBC has confirmed that Gervais will also star in Carell's last episode. He made a brief appearance earlier in the run, playing his UK Office character David Brent. Brent and Scott bumped into each other outside a lift and bonded over a shared sense of humour.
The Office season finale will air on May 19 at 9pm on NBC.
> Video: David Brent meets Michael Scott