Madano, established in 2004, specialises in corporate comms and public affairs. The firm represents clients in sectors including energy, building and infrastructure, financial and professional services, education and healthcare.
National is the largest PR consultancy in Canada and is looking to grow its footprint in the UK and Europe with the deal.
The terms of the transaction were undisclosed.
Madano founding partner Andy Eymond commented: 'Having access to international specialists in areas such as energy, infrastructure, professional services and health will provide a real competitive advantage to us.
'Moreover, we are delighted to be part of a group that has a great track record of building and nurturing communications businesses, as it has done in Canada, and are looking forward to playing a key part of the group’s strategic growth plan.'
National international managing partner Ralph Sutton said: 'Madano is a highly successful business with leaders who share our vision and long-term commitment to creating value for our clients. There is great synergy between our businesses that will help us expand internationally in key sectors.'
Madano was the 83rd largest UK comms consultancy in PRWeek's 2013 Top 150 report, with UK revenues of £2.1m after 21 per cent growth in 2012, and a UK staff of15.
National is owned by Res Publica Consulting Group, a Montreal-based marcoms holding company.