Under the scheme first-time buyers and home movers purchasing a new build property will be able to buy with a minimum 5% deposit, with the Welsh government contributing up to 20% of the purchase price.
The scheme, which provides buyers with a shared equity loan, is available for homes purchased up to £300,000.
Andrew Lewis, Monmouthshire Building Society chief executive, said: “We are proud of the support the Society is able to offer home buyers throughout Wales to help them pursue their dream of home ownership.
“The Society is pleased to commit to the Help to Buy - Wales scheme since it provides an affordable solution to home ownership for those who may find it difficult to save up for a larger deposit, as well as for existing homeowners who may be looking to move up the property ladder.”
Monmouthshire, based in Newport, are one of Wales’s largest and most successful financial institutions.
The new products include a 3-year discount rate mortgage of 2.75%, and a 3-year fixed rate product starting at 2.95%.
In the twelve months to 30 April 2013 Monmouthshire grew by 8.1%, with profit after tax reaching £3.1m.