The striker has penned a two-year deal at the Keepmoat Stadium.
Hiwula joined the Blues last October on a free transfer, having previously represented Coventry.
However, he was firmly third-choice striker at Fratton Park and was behind John Marquis and Ellis Harrison in the pecking order.
The ex-Huddersfield man was limited just 13 appearances in total, scoring three goals.
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He was not offered fresh terms by Danny Cowley at the end of the 2021-22 season and exited Pompey.
Now Hiwula has linked up with Doncaster ahead of the upcoming season.
He’s the second player to join Donny after leaving Pompey this summer.
Ben Close turned down fresh terms to remain on the south coast and instead opted to pen a three-year deal at the Keepmoat.