The governments of Samoa and Australia have signed an agreement in accordance with special World Trade Organisation guidelines for the accession of Least Developed Countries.
The deal will provide security of market access for a range of Australia merchandise exports including meat and dairy products, grains, and some electrical equipment.
Mr Crean says the outcomes will improve trading conditions for Australian exporters and help provide a secure basis for expanding exports.
On services, Samoa has made a range of commitments, including educational services, financial services, and legal advisory services.
A statement says a number of Australian companies are pursuing investment interests in Samoa's banking sector.
In 2007, Australia was Samoa's largest export destination and fourth largest source of imports.
The agreement will take effect when Samoa joins the WTO.
Samoa is still negotiating the overall terms of its WTO membership.