The development was announced by First Minister Nicola Sturgeon during a visit to the yard on Monday.
She said the contract would create new jobs at Ferguson and secure employment for the existing 150-strong workforce.
The yard went bust a year ago, but was taken over by entrepreneur Jim McColl who plans to invest up to £65m.
The deal, when finalised, will see the Ferguson yard build two vessels for the Caledonian Maritime Assets Ltd's (CMAL) fleet.
Ms Sturgeon said: "This is an excellent result for Ferguson Marine Engineering Limited and I am delighted to name them as preferred tenderer for the contract to build two new ferries, the largest commercial vessels to be built on the Clyde since 2001.
"This contract will see the 150-strong workforce retained and more staff taken on at the shipyard, underlining our commitment to creating the vital jobs needed to boost local economies and help stimulate growth across Scotland.
"The Scottish government is committed to supporting ferry users around Scotland by providing safe and reliable services, and this is the latest step to ensuring we have a fleet that continues to deliver for the communities that depend on it."
The Ferguson Marine shipyard in Port Glasgow has been named as the preferred bidder for a £97m contract to build two ferries to operate in Scotland.