Ultimo is marketing designs from its spring summer collection on the site. The move builds on the presence it has in selected House of Fraser stores.
The development comes as lingerie sales online outpace sales in traditional outlets across the industry.
Ultimo recorded its best December online sales in 2013, while House of Fraser saw online sales grow by 57.7% in the three weeks to December 28 compared with the previous year.
Ms Mone said: "Our growth strategy is focused on three growth areas: growing store presence, increasing our product offering and online expansion.
"We have seen online lingerie sales outpacing traditional sales channels, so we're thrilled to now be stocked on houseoffraser.co.uk where we hope to capitalise on this growing trend."