One of the most popular figures at the Memorial Stadium during his stint with Bristol and a previous winner of the 'Clubman of the Year' award, the 32-year-old prop-cum-hooker decided to make the short trip to Kingsholm after the Shoguns crashed out of the Premiership.
Johnstone was born to South African parents but an early move north by the family meant that the front row stalwart won 33 rugby caps for Zimbabwe before moving to Britain. After stints at Clifton and London Scottish, he joined Bristol where he has become one of their stalwart forwards.
He went on to win honours for Scotland 'A', just beating the deadline after which he would have been ineligible to play for his adopted country under the IRB 'Grannygate' rulings.
Johnstone, who made a successful switch from loosehead prop to hooker this season, has re-joined former Bristol coach Dean Ryan at the Cherry-and-Whites.
"I wish the Shoguns players and staff all the best for next season and hope to see them back in the Premiership soon," said Johnstone.
Johnstone's agent – Duncan Sandlant of GSM – believes that the move will be of huge benefit to both parties: "Paul is unusual in that he is equally adept at either loosehead prop or hooker. That, combined with his explosive speed, makes him a great addition to the Gloucester squad for next season," he said.