Whitewood Reff hopes to raise £125m by listing on the Main Market of the London Stock Exchange on or around 19 March.
The firm plans to use the money to offer profit-sharing loans to commercial property developments in the two countries. It said there was a "significant market opportunity" in Benelux, with leasing volumes at their highest rate since Q4 2012.
Newgate will handle PR during the IPO process and become its retained agency afterwards.
Whitewood Reff is Newgate’s latest account win involving a client that is preparing for flotation. Last month the agency announced it had been appointed by VPC Specialty Lending Investments, the peer-to-peer lending service, ahead of a planned IPO to raise £200m for acquisitions.