The "Grey's Anatomy" star shared the news on his official website and said that they are also expecting their first child together.
"Arielle and I are so happy to announce our marriage and new baby, who is soon to join our growing family. My kids are happy for us too and are looking forward to the arrival of their newest sibling!" McKidd said.
The Scottish actor shares 15-year-old daughter Iona and 17-year-old son Joseph with ex-wife Jane Parker, with whom he got divorced in December last year.
"There's much to be grateful for and we're thrilled for the adventures 2018 will bring us all!" he added.
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