Chris Jagger revealed the information during an interview on Portugal's Tele Jornal.
"He's doing a record at the moment in Los Angeles with Dave Stewart," he said. "He called me last night telling me what he was doing."
The album would be Mick Jagger's first solo effort in almost a decade, with the last being Goddess in the Doorway, released in 2001.
Dave Stewart made his name as one half of Eurythmics and first worked with Jagger in 1987.
The Rolling Stones frontman paid tribute to late soul singer Solomon Burke at last month's Grammy Awards.