The 41-year-old actress is said to have moved on from Chris Martin, her husband of 11 years. The couple in March announced that they were headed for a separation, reported Showbizspy.
Paltrow is believed to have met Leto, 42, at a party.
"Gwyn tried talking Chris into reconciling, but he wouldn't budge. That was the push she needed to move on. She's excited for the next chapter in her life and she has some guys in mind," a source said.
"Women swoon over Jared, and Gwyn definitely saw why when they talked. He totally charmed her. She thought he was one of the sexiest men she's ever met," the source added.