A U.S. bankruptcy judge approved the $9.2 million bid on Friday. The actor, dubbed "McDreamy" in the hospital TV drama based in Seattle, had claimed victory last week after an auction.
Dempsey said he was "thrilled that we prevailed."
"I've been deeply humbled by the outpouring of support from the city of Seattle and am very proud to be a new business owner in this amazing city," he said in a statement. "We have a lot to accomplish over the next few months and years, and I am excited to now call Seattle my second home."
But the company AgriNurture, that had teamed up with Starbucks to bid for the chain, filed an objection earlier this week. One group even claimed that Dempsey used his charm to win.
"Patrick is certainly charming. I don't know if he's that charming, but we won today because we have the best plan for the company," said Michael Avenatti with Dempsey's group, Global Baristas LLC.
Starbucks had wanted to buy about half of Tully's 47 shops in Washington and California and turn them into Starbucks stores, while the rest of the company would keep the Tully's name under the ownership of AgriNurture, which is based in the Philippines.
One reason Tully's owner TC Global Inc. didn't pick the Starbucks-AgriNurture deal was the complicated relationship Tully's has with Green Mountain Coffee Roasters Inc. Green Mountain owns the wholesale side of Tully's brand, which includes coffee in bags and single-serve packs that are sold in supermarkets and other stores.
Green Mountain preferred to keep the chain of coffee shops intact and operating under the Tully's name.
Tully's has more than 500 employees. Dempsey's group is buying all stores and will keep all employees as well as honor all pre-paid Tully's cards customers may be holding.
Following the Friday announcement, Dempsey took to his Twitter account posting, "We won!!! We won!!! Thank you Seattle! See you soon!"
The Associated Press contributed to this report.