Hayne, 28, quit the NFL after just one season to try to play rugby sevens for Fiji in this year's Rio Olympics.
The former San Francisco 49er previously played for Paramatta Eels in Australia's National Rugby League.
"I thought the boys needed a bit of added competition," said Fiji coach Ben Ryan.
"Jarryd has trained well. In attack he is comfortable on the ball, he has good spatial awareness and has good footwork. In defence he is a good tackler."
Fiji need eight points to claim this season's World Series title.
Hayne, who joined the Fiji camp as an injury replacement, left Australia's NRL in 2014 to pursue a career in the NFL as a running back.
He played international rugby league for both Australia, where he was born, and Fiji, who he qualifies for via his father.
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Former NFL and rugby league player Jarryd Hayne is in Fiji's squad for this weekend's final round of the World Rugby Sevens Series in London.