That's what Spurs' Sandro Mamukelashvili did to his family's car ... replacing their old SUV, a black Nissan Murano with a brand new electric car ... and the surprise was captured on video!

The Spurs forward, who starred at Seton Hall University, re-signed with San Antonio (1 year, $2 million) in March -- and he's putting his money to good use ... copping a white electric Volkswagen ID4.

Sandro's family was extremely happy and even took the new whip out for a spin.

"Surprising my family with a new car," the 24-year-old wrote on Instagram. "I’m so blessed to be in this position. MAMU FAM 💪🏼❤️."

The story is extra sweet because the family has been through a lot. Sandro's dad Zurab is a cancer survivor ... and he was living overseas in Georgia while Mamu was hooping at The Hall. In 2020, when #16 ranked SHU was playing #21 ranked Butler at The Rock in Jersey, Mamu knocked down an incredible game-winning shot ... and it happened to be the first game his dad was able to attend in nearly a year.

"As soon as he drew up the play, I was like, “I’m gonna make this.” When I did, all I did was stare at my father the whole time," Mamu told the NY Post at the time.

"He was pointing at me, and I was pointing at him. I feel like it was one of the proudest moments he had."