The former Big Brother star was snapped with her little girl at the special event, which was held to celebrate the updating of the classic Miffy storybooks, written by Dick Bruna almost 50 years ago.
During the party, Imogen took part in the recording of a short film, which saw her read an extract from one of the books.
Imogen, 31, dressed smart but casual for the event, opting for ripped jeans, a cosy jumper and a pair of Converse trainers.
The mum-of-one wore her hair half up and half down and glammed up her daytime look with a slick of bright pink lipstick.
Ariana, meanwhile, looked cute as a button in a cream and grey outfit - not to mention her sweet little hair bow!
On Saturday, Ariana was, however, dressed a little more traditionally to mark St David's Day.
Welsh-born Imogen shared four cute photos of her one-year-old on Instagram, telling her followers: "Happy St David's day....my little Welsh lady celebrating #tradition #march1st #welsh #proud #patriotic."
Dydd Gwyl Dewi Hapus, Imogen and Ariana!
Celebrities who have welcomed babies in 2014:
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