Saints have boosted their scrum-half ranks ahead of the new season.
James Mitchell, elder brother of reigning Northampton young player of the year Alex Mitchell, has joined on a short-term deal.
The 24-year-old has impressed during a trial period at Franklin's Gardens this summer and has now penned a contract that will keep him at Saints for the duration of the Rugby World Cup.
Saints required more options as Cobus Reinach is in South Africa's squad for the tournament in Japan, while Alex Mitchell will be sidelined until November with a knee injury.
James Mitchell's most recent club was Connacht, where he scored two tries in 26 appearances during a two-year stay.
He moved to the west coast of Ireland from Sale Sharks, where he came through the Academy.
James Mitchell has represented England at Under-16, Under-17 and Under-18 level before getting selected for the 2015 Under-20 Six Nations.
He played in all five games during the Championship and subsequently played every match in the Red Rose’s run to the final of the Under-20 World Championship in Italy.
And he will now be competing for starts with Henry Taylor, who joined Saints from Saracens during the summer, and youngster Connor Tupai.
Saints host Leinster in a pre-season friendly at the Gardens on September 12 before starting their season with four Premiership Rugby Cup matches, beginning with a trip to Sale Sharks on September 21.
The Gallagher Premiership campaign starts at champions Saracens on October 19.