The group, which provides homes and services to more than 200,000 people in 17 local authority areas across central Scotland, has netted £185 million of new funding from the European Investment Bank (EIB).
The latest round of funding brings the total private investment raised by Wheatley since 2013 to £800m.
The EIB loan – the largest of its type made in Scotland – is linked to a commitment by the group to invest £400m over the next three years in affordable housing.
This includes refurbishing existing homes to meet new Scottish and EU energy-efficiency standards, as well as housing and integrating refugees into existing communities.
The landmark deal was announced in Glasgow by EIB vice president Jonathan Taylor at a community event attended by First Minister Nicola Sturgeon and tenants, staff and apprentices from across Wheatley.
Wheatley chair Alastair MacNish said: “This loan is fantastic news for people and families across Scotland and is a huge vote of confidence in Wheatley and our unyielding commitment to affordable housing.
“It will help us to consolidate our position as the UK’s largest builder of social-rented homes, which we hold close as a badge of honour at a time when the availability and supply of affordable housing is such an acute priority.”