The Voice host marked the occasion by donning a black bodycon dress from her range and posing with models wearing some of her other designs at Claridge's Hotel.
Speaking at the afternoon tea launch event, Willoughby told Heat: "The range itself I'm incredibly proud of. I've worked with Very for three years now and I think that this one is my favourite yet.
"This is a really proud moment for me, actually. Whenever you've been working on something for a long time and it all comes together... and lots of gorgeous girls are wearing your clothes, it's a really lovely thing."
The collection is Willoughby's eighth with Very and has been described by the fashion outlet as "feminine and flattering".