The Parks and Recreation star told E Online that his relationship with Mullally allowed him to continue with his acting career during a long period of unsuccessful auditions before securing his spot on the NBC comedy.
"Meeting Megan pretty much made my life amazing. I was pretty happy biding my time looking for my dream job, and she by far is the most supportive element of my life," he explained.
"She really always kept my confidence up and she coaches me in my auditions. When I finally got the part of Ron Swanson, I was so grateful all of these other crappy TV shows that I had tested for [didn't hire me] - I was like, 'Thank God, the universe saved me for this job'. I could not have written a part that was so much my dream part. I could not have even fathomed that it exists."
Mullally reprised her recurring role as Ron Swanson's ex-wife Tammy in the Parks and Recreation season finale.
The couple met in 2000 while performing in a play together in Los Angeles. They later married in 2003.