The pair were spotted dining together in L.A. at exclusive restaurant Soho House and apparently looked very cosy.
According to The Sun, Katy was pulling out all the stops to impress Mr Pattinson.
An onlooker told The Sun: "She was laying on the charm, playing the minx- tossing her hair back, laughing at his jokes, touching his arm and twirling her hair."
"She was sat across from Rob but later moved next to him."
[Related story: Kristen Stewart dropped from SWATH sequel]
[Related story: Robert Pattinson spotted for first time since split]
Katy may have been flirting into overtime; however, it seems that Rob was more interested in something else she had to offer.
The onlooker stated: "She wore a tight, sparkly top and Rob was looking at her breasts all night"
"He tried to avoid it when talking to her but as soon as she looked away to talk to someone else, Rob would sneak a peek."
Now, now Rob- that's no way to treat a lady!
Katy is allegedly back on the singles market after a brief romance with Jennifer Aniston's ex John Mayer while Rob has only just returned to the public eye after Kristen Stewart was revealed to have cheated on him.