Johnson announced their engagement with an Instagram post on Sunday, saying: "Boys are on!! The only yes I need."
The post has over 21,000 likes and thousands of comments - including from former teammates Chad Townsend, Kevin Locke and Bodene Thompson.
Other photos have since emerged on social media of the pair celebrating with friends and family.
The pair had been in a relationship since early 2016.
Johnson was in a moon boot and on crutches in the photos, after injuring his ankle during the Warriors 26-4 over the Wests Tigers on the weekend.
He is expected to miss their next match against the Roosters in Auckland.