The 46-year-old Australian will join New Zealand Rugby Union's coaching team once Saracens' post-season involvement in the English Zurich Premiership is over. He joined the club last year.
NZRU high performance manager Mike Chu said: "Mick Byrne is a vastly experienced coach with an impeccable track record.
"He is the latest addition to the team of specialist coaches and sports science experts who are tasked with honing specific skills or key areas.
"We want to ensure the All Blacks and the elite players coming through have everything they need to perform at their best."