The Bangor-based developer and builder revealed this morning that the Cardiff scheme and another in Belfast have been forward sold to institutional investors.
The deals pave the way for the builder to start both schemes, which are due for delivery in August 2018.
In Cardiff city centre, the Bridge Street development will provide over 470 beds for students.
Retail and commercial units would be developed on the ground floor using existing buildings on the site and a new alcohol treatment centre will be built, replacing an existing facility.
The site located on land bound by Bridge Street, Charles Street and Wesley Lane already has planning consent.
Watkin Jones also has consent for a separate 42-storey student tower at Custom House Street in Cardiff, which is set to become Wales’ tallest building.
The Belfast project, which also comprises retail and office space, involves demolishing buildings on the capital’s Queen Street, to build a 14-storey, 340-bed student room project.
The existing building facade will be retained at Queen Street.
Mark Watkin Jones, Chief Executive Officer of Watkin Jones, said: “We are delighted to announce today that we have forward sold our developments in Cardiff and Belfast to two institutional investors in purpose built student accommodation, which further underpins the visibility of our earnings and cashflow.
“The interest in the sector remains strong.”