His on-off love Paris Hilton looked smitten during their appearance at the Venice film festival after the couple's tour of the shopping district and sights earlier in the day.
They have recently united following a cooling off period in June.
The American socialite called off their romance following an argument and was then seen enjoying the attentions of Cristiano Ronaldo in an LA nightclub.
Perhaps to underline that he's the only man on the scene at present, 23-year-old Doug was making a special effort at the weekend.
Witnesses report that the former baseball ace treated her to jewels from Cartier.
One onlooker said: "Doug whipped out his black Amex card and took Paris on a major shopping spree.
"They went to Cartier where he bought her the entire diamond Panther collection of rings, necklaces, and bracelets".
It's not clear if any of the gems were on show at festival. The heiress was certainly dazzling in a floor-length sequinned affair and plenty of ice as she arrived hand-in-hand with her beau, who was dashing in a smart suit.
The evening ended with them kissing and canoodling at a party on star designer Alberta Ferretti's yacht.