The actress, 40, who was recently rumored to be back together with John Mayer, has a guest-starring role on 'Cougar Town'.
"She seemed very excited about her date," People Magazine quoted an onlooker as saying.
"She and Josh sat at a more private table and they seemed to get along great.
"It was obvious that they don''t know each other well, but there was a flirty energy between them and Jen looked very happy," the witness added.
However, reps of both stars haven''t commented on the relationship.
"Jen has been in the best mood lately," a source said.
"She is trying to do whatever makes her happy, which includes going on fun dates with interesting men," the source added.