The Edinburgh-based oil and gas group hired Brunswick after a competitive pitch, managed by its float advisers Cazenove and Credit Suisse First Boston.
Neither Wood Group nor Brunswick would comment on the appointment, but it is understood Brunswick was selected from an initial shortlist of six agencies.
Brunswick is believed to be working on a specific IPO mandate, communicating to analysts, the financial media and potential investors.
Wood Group, which did not retain a financial comms agency prior to Brunswick, is expected to list on the London Stock Exchange in the next two months.
Brunswick has been hired on an initial project brief to handle all comms for the float, but it is expected the account could be reviewed with a view to extending the relationship following the listing.
Agency partners Jon Coles and Patrick Handley are heading the brief, reporting to Wood Group head of corporate comms Carolyn Smith.
Wood Group, led by founder chairman and CEO Sir Ian Wood, is hoping to raise £138m through the IPO to reduce company borrowings and fuel further acquisitions.
Meanwhile fellow financial PR shop Hudson Sandler is stepping up its work for DIY chain Focus Wickes, which announced its own plans for a summer IPO this week, valuing the firm at up to £1.5bn.
The UK's second largest DIY chain, which first hired Hudson Sandler to raise its profile in the City at the end of 2000, has tasked the agency with communicating its business strategies and objectives to potential investors.
Hudson Sandler director Andrew Hayes, who is leading the account, said the work involved media relations and strategic comms advice to the Focus Wickes board.
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