The newlyweds and fellow guests were stunned when Tim stepped out onstage at the Vie venue dressed in a classic black tux, and serenaded them with a few songs, including fan favourite Live Like You Were Dying.
One member of the wedding party posted footage of Tim's sing-along performance on Instagram and added the hashtag caption "#asgoodasitgets".
McGraw gave the new Mr and Mrs. Paul Getz a really good start as a married couple - he and his wife Faith Hill will celebrate their 20th anniversary on 6 October (16).
Tim wasn't the only singer thrilling wedding guests over the weekend - Bruno Mars entertained at Spotify founder Daniel Ek's wedding to Sofia Levander, where comedian Chris Rock officiated.
The nuptials took place on Saturday night (27Aug16) on Lake Como in northern Italy, and featured guests including Facebook billionaire Mark Zuckerberg and his wife Priscilla Chan, and Swedish explorer Johan Ernst Nilson.
McGraw and Mars' wedding performances come just weeks after Jon Bon Jovi grabbed the mic at a friend's wedding in Florida last month (Jul16), when the group struck up a jazzy version of his hit Livin' on a Prayer, and Usher added wedding singer to his resume on 23 July (16) after joining a former American Idol contestant to serenade a pair of newlyweds.
The Confessions hitmaker was a guest at Miami Heat basketball boss Nick Arison and Jenna Green's nuptials when the best man, Justin Bieber's manager Scooter Braun, requested the wedding band B. Random play an Usher track.
The group, fronted by one-time Idol contestant and Usher backing singer Brandon Rogers, then encouraged the superstar to take over the mic, which he happily obliged, trading verses on Yeah!.