The Soweto giants announced the news on Monday. The deal is subject to a medical.
Mlambo played a pivotal role helping the Clever Boys win the league and MTN 8 last season.
Mlambo’s move to Bucs is a long anticipated one since Pirates have been keeping the tabs with the 26-year-old.
Pirates say fans can expect further announcements as the club looks to beef up the squad as the season enters its final stretch.