The voluntary group is spending £10,000 on a poster campaign across London and the South East emphasising that the union's work stretches beyond village fetes and into gritty social issues such as prisons and child contact centres. It also provides holidays for low-income families and runs parenting courses.
The union has more than one million members worldwide, including 122,000 in the UK. Clare Berry, head of marketing at the union, estimates that if it wasn't for the organisation's "twee" image, the figure would be even higher.
"What has held people back from joining the union in the UK is the name and its perception," she said. "If we could change this, the membership should increase."
Contrary to popular perception, Mothers' Union members don't have to be mothers, married or even female. They do, however, have to believe in the Christian objectives of the organisation and be baptised.
"We are trying to let people know that if they want to be involved in changing and influencing family life, then they can do so through the Mothers' Union. If your passion is for family life, this is the organisation that you should know about," said Berry.
The ad campaign began on 17 March and will run for three weeks. A billboard will be displayed on the A4 in London and smaller posters will be exhibited on train routes out of London's Victoria station.
The primary theme of the campaign, which aims to recruit members and raise funds, is the heart, and the message is that the heart of the union never stops working.