Katharine McPhee was a vision in white on her wedding day.

The "American Idol" star, 35, tied the knot with music producer David Foster, 69, in London on Friday.

For her very special day, McPhee wore a custom designed strapless gown by American designer Zac Posen. It featured layers of tulle, a sweetheart neckline, and matching veil.

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The Broadway star gave fans a first look at the stunning gown on Instagram Stories while in a car with her mom Patricia.

Katharine McPhee (L) shows off custom Zac Posen wedding dress 

Katharine McPhee (L) shows off custom Zac Posen wedding dress  (Instagram Stories )

McPhee started the hunt for the perfect dress in January with her stepdaughter Jordan Foster, who also happens to be the youngest of Foster’s five children.

Foster proposed to his bride in July 2017 with a huge emerald diamond ring while the couple was on vacation in Italy. The couple first met in 2006 when McPhee was a contestant on season 5 of "American Idol" and Foster was a mentor on the singing-competition series.

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"We genuinely love and respect each other and have for a very long time,” McPhee told People magazine.

Katherine McPhee and David Foster, pictured here in May, tied the knot in London on Friday.

Katherine McPhee and David Foster, pictured here in May, tied the knot in London on Friday. (Bennett Raglin/Getty Images for Breast Cancer Research Foundation, File)

"Her special day finally came and it was everything she could have imagined it would be. It was a long time coming and this one just felt right to Katharine," a source told Fox News on Friday. "Regardless of what other people have said about her and David’s relationship – it was more than a decade in the making and she’s happy."

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This wedding marks Foster's fifth marriage and McPhee's second.