McKie joins Mouchel from BT Global Services, where he worked as a senior strategy associate on the controversial £2bn national IT programme for NHS hospitals and GPs' surgeries.
The group said that McKie would take responsibility for 'building a positive external image for Mouchel's businesses and raising its profile with key stakeholder groups, including the City, industry, partners, clients and the media'.
In August the group said it expects full-year results to be in line with its expectations.
Mouchel said demand for its services remains strong and its future prospects are underpinned by a healthy bidding pipeline worth £2.2bn.
McKie was previously communications director at the Government's high-profile rail agency, the Strategic Rail Authority.
He spent much of his earlier career at the Department for Transport as chief press officer, and at the Downing Street press office.