Alban was founded in 1978 and has built up a client list including Unilever, Nestle and Masterfoods.
The outdoor firm will join the Posterscope Worldwide's family of companies, including Philippine-based JKJ Media, which was acquired by Aegis in June making Posterscope the largest group in the region.
Robert Lerwill, chief executive of Aegis Group, said the acquisition of Alban will further strengthen Posterscope's position in the market.
"Aegis is committed to growing Postercope's presence in all major markets. The acquisition of Alban underpins Posterscope's strong position in the UK," he said.
The £8m purchase price will be payable over three years subject to performance criteria.
Posterscope is the market leader in the UK outdoor market with billings of £350m and 42% market share.
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