Released by the Lord's club at the end of the 2022 season, the 30-year-old spent a period on loan last term during the T20 Blast
Durham have signed Nathan Sowter on a one-year deal.
The Australia-born legspinner was released by Middlesex at the end of the 2022 season after seven years at the club.
Sowter was loaned to Chester-le-Street mid-way through last term's T20 Blast and played seven times, taking eight wickets.
During seven years with the Lord's club he made 106 appearances across formats, claiming 127 scalps.
"I am really excited for this opportunity to come back to Durham after a short loan spell last season," he said.
Sowter took 107 wickets in white-ball cricket for Middlesex (Alex Davidson/Getty Images)
"I am looking forward to making an impact and contributing to success on the pitch with Durham."
It remains to be seen if Sowter is available in the Royal London Cup having been part of the Oval Invincibles squad for the past two campaigns of the men's Hundred.
Director of cricket, Marcus North added: "It is great that we have been able to secure Nathan Sowter to Durham for next season.
"Nathan impressed during his loan spell in the summer and will bring a wealth of experience and quality to complement our current spin options in the shorter format."
The announcement comes a week after Ryan Campbell was appointed head coach on a three-year deal, following the departure of James Franklin at the end of last term.
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