Kutcher is to play internet billionaire Walden Schmidt in the relaunched show, following Charlie Sheen's dismissal earlier this year (11).
Now Greer, who starred in 2008 comedy Miss/Guided, which Kutcher co-executive produced, has joined the cast, playing Schmidt's soon-to-be ex-wife.
According to The Hollywood Reporter, Kutcher's character will become so depressed about his divorce that he buys the house that was formerly owned by Sheen's late character and begs the present occupants to stay.
Cryer says, ""My character ends up being the more romantically experienced one of the two of them. So Alan becomes sort of a mentor character to Ashton's character. And as bad as an idea as that sounds, it's just as bad on the show - I'm a terrible mentor. And that's where a lot of the fun of the show comes from.""
Greer also previously appeared on the show in a bit-part playing a love interest of Sheen's character in 2007.
The ninth season of the series will launch in the U.S. on 19 September (11).