The legendary songstress spoke with ET's Lauren Zima at the New York premiere of her new documentary concert film Madame X, held at The Edition Hotel Times Square on Thursday.
Madonna said she spoke with Spears over the phone earlier in the day, and was "just checking in on her, and congratulating her on her marriage. Or her pending marriage."
"I love her," Madonna added with a smile.
Spears recently revealed that she was engaged to boyfriend Sam Asghari, following months of very contentious legal drama with her father over her years-long conservatorship. During the high-profile courtroom battles, Madonna had frequently spoken up to share her support for the singer and the fan-driven #FreeBritney movement.