It is buying them in two tranches, the first eight on April 2 and the other seven on or before July 2.
The new outlets, suited to tenanted estate management, will increase Belhaven's total estate to 128 pubs, 40 managed and 88 tenanted houses.
Belhaven has also agreed an exclusive deal to supply beers, soft drinks and ciders to Maclay's 17 Scottish pubs and its associated Enterprise Investment Scheme companies for five years. It has agreed to buy some of Maclay's wholesale assets.
The two have also agreed a five-year licensing agreement for Maclay brands in Scotland with a commitment from Belhaven to supply all Maclay customers with their existing range, maintaining existing supply arrangements.