Hignett only left Boro's coaching staff in the summer to follow Colin Cooper to neighbours Hartlepool United.
But now he has made a quick return to The Riverside ranks, having agreed to become Aitor Karanka's new assistant.
Youth coach Jamie Clapham had been filling in, but now the club have appointed Hignett and so the former Ipswich defender will return to his role of looking after the club's Under-21 side.
A Hartlepool statement confirmed the news and read: brief Pools statement read: "The Club wishes to advise that late this afternoon Assistant Manager Craig Hignett has handed in his notice.
"Middlesbrough Football Club have advised the Club's Chief Executive Russ Green that Craig will not be working his notice period for Hartlepool United and will be starting work at Middlesbrough on Tuesday 4th March.
"The Club has no further comment."