The musical pair, who celebrated their 21st anniversary last November, say they pray before every performance together.
Speaking with PEOPLE magazine, Hill said: "Tim and I share a quick quiet moment together before hitting the stage. Always praying."
McGraw, 51, and Hill, 50, met in 1996 when Hill performed an opening act on McGraw's Spontaneous Combustion tour. They married in October of that year.
The pair, who have embarked on their Soul2Soul World Tour, say they still make date nights a priority, despite their hectic schedules.
They have three daughters aged between 16 and 21.
McGraw and Hill recently released their first album of duets. They previously sang together 'Keep Your Eyes On Me' for the film adaptation of The Shack.
Speaking about the importance they place on time on their own, Hill added: "We both have our daily routines and we have our own dressing rooms.
"We each have our own space to retreat to so we do get time to ourselves."
McGraw said: "Funny, as we get older it's less about the big gestures and more about just spending the time together at home.
"For our 20th wedding anniversary, we stayed home, in our pyjamas and watched TV. We loved it."
Stay up to date with the latest news stories from a Christian perspective. Sign up to our daily newsletter and receive more stories like this straight to your inbox every morning.