The Illawarra junior ignored overtures from the Super League to continue his career in Australia.
"Josh is a good competitor, a great trainer and does a lot of wonderful work in the community," Newcastle coach Nathan Brown said.
"These are all qualities on and off the field that are important to have around our young squad."
Starling joins fellow Manly outcast Jamie Buhrer in Newcastle.
The Knights have also been linked in the local media with a deal involving a potential trade for prop Jack Stockwell.