The 19-year-old has featured for the Posh's Academy setup since making his move from Nottingham Forest in 2020.
At the end of the 2021/22 campaign, Darlington signed a two-year professional development contract with Peterborough United which saw him progress from the U18s to the U21s
Last season, he joined Northern Premier League club Corby Town on loan where he made four appearances.
Darlington will go into contention for their season opener against Gresley Rovers on Saturday.
Cambridge City have also confirmed the signing of Bradley Rolt from Spalding United.
Like Darlington, Rolt is also a centre-forward and was a former Peterborough United youth player.
The 20-year-old has enjoyed spells at Brackley Town, Braintree, Bohemians and most recently Spalding United.
He made 34 appearances for The Tulips and scored ten times.
Photo credit: Peterborough United
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