Unity won the business following a competitive pitch against undisclosed agencies. It is not known if the incumbent on the account, Return on Digital, repitched for the business.
The agency has been tasked with growing Wonderbra's presence online and increasing its relevance among its target audience.
It will be creating the social media component of a brand campaign due to launch later this year and will be in charge of driving traffic to Wonderbra's newly launched ecommerce site.
The appointment does not affect Iris PR, which holds Wonderbra UK's PR business.
Wonderbra's marketing is largely PR and digitally led. In December last year, the brand staged a bungee jump outside Battersea Power Station to promote its Ultimate Plunge Bra.