The Fringe star said that he and Kruger are perfectly satisfied with their relationship after six years together.
Jackson told Life & Style: "Neither of us is religious, and the picket fence isn't what we're aiming at. We're together for six years now, so for all intents and purposes, we are [married]. I have no need for a priest to tell me that!"
He went on to suggest that there's "no recipe" to maintaining a rewarding relationship.
"Just make sure you put the work in," Jackson advised.
Kruger has made similar comments about tying the knot in the past, such as saying in 2011 that commitment should only be made in the heart.
The Inglourious Basterds actress was married to French star Guillaume Canet for five years, but they split in 2006.
Watch Joshua Jackson in the trailer for upcoming film Lay the Favourite below: