The former RTE 2FM host and Frank tied the knot in front of friends and family.
Nikki took to social media to share the good news that she was finally "Mrs Black".
Hours previously, she was mixing cups of Lyons tea with glasses of champagne as she got ready for her big day.
The couple have been in a relationship since 2010, and have a two-year-old daughter Farrah together.
Donegal man Frank popped the question to the radio star in 2012 when he whisked her away to the five-star Lough Eske castle.
"I was just oblivious to everything. I was walking up the steps of the tower to have a look over the lake and I turned around at the top and he was down on one knee," Nikki said at the time. "I literally couldn't speak for about 10 minutes, I was so shocked.
"It was completely unexpected. He had gotten the whole tower blocked off and it was all lit up with candles. It was lovely and romantic, so there was lots of champagne for us that night."
Nikki (36) said she "just knew" he was the right man for her from the very start.
"You do know when you meet the right person. It's completely different to any other relationship I've ever had and everything's just easy with him -- he's definitely the one," she said.