From today it will lend to landlords investing in properties in Edinburgh, Glasgow, Dundee and Aberdeen.
The lender is also set to join the panel of the Intrinsic network which has many of its partners based in Scotland.
Keystone managing director David Whittaker says: “There is an opportunity to help landlords north of the border where demand for rental properties remains strong, especially in the main cities and that’s where we will be focusing our efforts.”
Keystone’s funding is provided exclusively by Aldermore Bank, which started lending in Scotland in May.
Aldermore managing director of commercial mortgages Rob Lankey says: “Lending in Scotland has proved a great move for Aldermore Mortgages and we felt that offering the same reach to Keystone would widen the borrowing options to investors who have often struggled to secure finance in the region.”
Buy-to-let brokerage Mortgages for Business and Aldermore launched Keystone in April 2012.