Thisara Perera will fill in as one of Gloucestershire's overseas players at the start of the Vitality Blast.
Sri Lanka all-rounder Perera deputises for Australian white-ball specialist Andrew Tye for the first two matches.
He returns to Bristol, having played for the club in the shortest format in 2017, and will add international quality alongside captain Michael Klinger.
Perera - a veteran of 73 Twenty20 international caps - hit the winning runs in the ICC World Twenty 20 Final in 2014.
The 29-year-old is a renowned late-order hitter and canny seam bowler.
"Having a player of Thisara's quality join the club is a huge coup for Gloucestershire," said chief executive Will Brown.
"He played well for us last year and we know that his experience playing in both the Big Bash and the IPL will be invaluable in the opening away fixtures."
Perera was due to travel to matches against Somerset and Middlesex before passing the baton to Tye for the first home match versus Kent Spitfires in Bristol next Wednesday.
Gloucestershire are 1212/1 to win the Vitality Blast and 1212/1 to win the County Championship Division Two title.
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