McNamara was previously president of Alterian's online division and CEO of Dynamics Direct Inc, the e-marketing software firm acquired by Alterian in May 2006.
McNamara said: "I am delighted to take up the role of chief marketing officer at this exciting time in our development and look forward, together with the first-rate marketing team we have created, to helping drive our growth."
McNamara will be based in the US for the role, and presides over three new marketing recruits, Bob Hale, Joe Stanhope and Bob Barker, the only recruit working in the Bristol headquarters.
Hale becomes vice-president of business development, with a remit to generate increased interest in Alterian's marketing services platform. He also came to Alterian through the acquisition of Dynamics Direct Inc, where he held the same role.
Barker joins Alterian as vice-president of corporate marketing, another newly created position, tasked with developing communication activity. His software marketing career spans 20 years, and he joins from SAS, where he was marketing director.
Stanhope has been appointed director of global product marketing, following his successful tenure as director of marketing for Alterian North America.
David Eldridge, CEO of Alterian said: "Alterian is in an excellent position to continue our strong growth -- with the ongoing roll-out of our partner distribution model, the growing demand for our product range globally and the new market opportunities presented by our recent acquisitions."