The 37-year-old actress, who was previously married to rockstar Chris Robinson, was seen sharing a kiss with the Chief band's guitarist, a source told People magazine.
"Kate had his arms around him and they kissed. They definitely looked like more than friends," the source added.
The rumoured couple had lunch together at a cafe before heading back to Hudson's house.
They were also seen getting cosy at the Santa Monica restaurant Giorgio Baldi.