Lord Chadlington's acquisitive PR group will initially pay £7.2m in cash and £4.8m by the issue of shares. This figure could rise to £35m over the next three years.
In a separate deal, Huntsworth has also agreed to acquire London corporate advisory shop Quiller. The initial payment is £5.9m (£4.2m of which being cash), with a maximum total consideration of around £10.7m.
MMD operates in 18 markets including Russia, Turkey and Kazakhstan. Its chairman Alistair McLeish will continue to operate the business following its sale to Huntsworth.
Quiller was founded in 1998 and provides corporate comms, issues management, litigation support and PA consultancy. It will retain its brand but will join Huntsworth's Hudson Sandler business.
Nine-strong Quiller's chairman Jonathan Hill said: 'Strategically and culturally, Quiller and Hudson Sandler are an excellent fit.'