The Oscar-nominee sparked rumours he had split from actress Lane following a cosy coffee date with Shelton in Santa Monica, California last week (28Apr10), when he was pictured without his wedding ring.
The pair was then photographed hugging before sharing a friendly kiss as they parted ways.
But Brolin's spokeswoman Liz Mahoney has played down the encounter, insisting the stars, who worked together in movies such as Grindhouse and W, are nothing more than pals.
She tells the National Enquirer, "Josh and Marley are dear, dear friends. They've done three movies together and this was just an embrace between old friends."
The meeting took place just two days before Shelton was arrested on suspicion of driving under the influence (DUI). The Sin City actress was taken into custody on 30 April (10) after being pulled over by cops in Hollywood and failing a sobriety test. She was freed on bail on Saturday (01May10).
Brolin has been married to Unfaithful star Lane since 2004, while Shelton wed her producer husband Beau Flynn in 2001 and welcomed their first child together last September (09).