The Spurs would not release details of the extension, but league sources told ESPN on Monday that the three-year deal is worth $72.3 million.
"I'm happy to be here," Aldridge told reporters Tuesday. "It worked out for both sides. I feel like this preseason has been great for myself. Trying to find my rhythm, be myself. I feel like the offense has had some tweaks where I'm feeling more comfortable, helping the team. Pop [coach Gregg Popovich] told me he was happy about it."
The extension will keep Aldridge, 32, under contract with the Spurs through the 2020-21 season. It includes a partially guaranteed salary in the deal's final season, league sources told ESPN. Only $7 million is guaranteed in the final year of the extension, league sources told ESPN's Zach Lowe.
"This place is great, great organization. They do things the right way," Aldridge said. "Talks this summer were very constructive. ... I like that Pop has been great about what I needed or wanted. So far, it's been great."
The contract extension culminates what had been two often-turbulent seasons between Aldridge and the Spurs since his arrival as a free agent from Portland. The deal reflects the Spurs' desire to continue surrounding Kawhi Leonard with talent and Aldridge's increased comfort with the franchise.
Aldridge will opt into the $22.3 million player option on his 2018-19 contract, and the extension's new terms will start with the 2019-20 season. Aldridge is set to make $21.4 million in the 2017-18 season.
San Antonio did discuss trade scenarios with teams centered on Aldridge prior to the draft and during the summer but never found an offer that intrigued them enough to make a deal, league sources said.
At times, Aldridge hasn't been happy with the franchise, and the franchise hasn't been happy with him. Nevertheless, Aldridge arrived in training camp in strong shape and with a better relationship with Spurs coach Gregg Popovich, and both sides understand that the uncertainty of free agency next summer could make an extension a wise option.
San Antonio didn't have a better alternative available in free agency to partner with Leonard, and Aldridge couldn't be sure that he'd be able to find this kind of long-term financial score available on the free-agent market.
Aldridge averaged 17.3 points and 7.3 rebounds for the Spurs a season ago. He has averaged 19.1 points and 8.3 rebounds in his 11-year NBA career.