The 75-strong chain, which operates c-stores and CTNs in the north of England, the Midlands and South Wales, bought the 2,500 sq ft store in Armley, Leeds, from an independent retailer. The store has sales of around £31,000 a week.
All 15 staff have been kept on and trained on the retailer's Challenge 30 policy on age-restricted products, said MD Nigel Mills.
A temporary sign is in place at the store and a full refurbishment is planned in the next three months to increase the store's fresh and chilled offering.
Mills Group revealed in November last year that it planned to acquire six sites in 2009. Before the acquisition of the Armley store it had acquired just one new site in the past five years and disposed of 13.
Mills added he was confident he would find the remaining five stores. He has retained a property agent in South Yorkshire to hunt for sites east of the Pennines.
"I'm fairly optimistic," he said. "The fact that we have him out looking for potential acquisitions makes me all the more positive."