Though the headline-making pair may have been intoxicated following the Grammy Awards, where Barker performed on Sunday, April 3, Diamond maintained they were more than OK to become man and wife.
"They had" been drinking, he pointed out to the outlet, "But you know what I'm looking at is how they say their vows. How clear is their speech? Their speech was extremely clear and Travis is looking at her, you know like the way I look at my wife."
"He [Travis] wasn't saying as much as her [Kourtney], but he was speaking with his eyes, the way he was looking at her like, 'Wow, I get to marry you"" Diamond, 69, shared of the couple — who did not recite their own vows but rather used "Elvis vows" — after their quick wedding.
"It was an honor, they were like kids in a candy shop walking in. You see these two beautiful people, they're really well known and I get to do their wedding," he continued to the outlet. "It was really special."
The "Burning Love" vocalist look-alike noted that he almost turned down the Poosh founder, 42, and the Blink-182 drummer, 46, after being called to perform the ceremony out of the blue in the early morning hours.
"It was like 12:30 at night and they wanted me to be down there at 1 o'clock, then he called me back and said, 'No, they're gonna be late, it's not gonna be till 2,'" Diamond explained.
"I almost changed my mind I said, 'I don't know if that's too late because I've got weddings the next day,'" he continued, adding that he caved when the offer was made a bit bigger. "'We'll sweeten the pot, we'll give you more money, it's going to be a celebrity,'" Diamond recalled of what he was told about the couple.
The entertainer admitted he had no clue who the musician was but was aware of the reality star. "I'm not familiar with Travis's band but I've heard from my son he's amazing, of course everyone's a fan of the Kardashians," he said, confessing he however "never watched the show" himself.
Although Kardashian and Barker are now married "in the eyes of God" and will later have a huge ceremony, the two have not obtained an official marriage license.
"I marry people all the time in commitment ceremonies," Diamond reportedly noted. "They don't have legal papers, but when two hearts are joined together in holy matrimony and when they really love each other, to me, it's a marriage. And in the old days they didn't have paperwork."
The couple is expected to be planning "several" more celebrations of their union in the near future.