The federal Finance Department said Thursday the province has signed a memorandum of agreement to join the Co-operative Capital Markets Regulatory System.
The addition of P.E.I. follows a decision in July by Saskatchewan and New Brunswick to join B.C., Ontario and the federal government in establishing a national regulator.
Canada is the only G20 country without a national securities regulator.
The Finance Department said the participating jurisdictions will continue to work together to encourage the remaining provinces and territories to join the system.
Alberta and Quebec have remained staunchly opposed to a national regulator.
Under the current system, all 13 jurisdictions in Canada regulate their own capital markets and bond and securities issuances, although all except Ontario also belong to the so-called passport system by which the approval of one commission essentially allows for registration in another province.
In September, the partners released consultation drafts of uniform provincial capital markets legislation and the complementary federal legislation for public comment.
A national regulator will administer a single set of regulations under the proposed rules and would be funded through a single set of fees.
Ottawa has long championed the idea of a national securities regulator, but the Supreme Court sided with the provinces in 2011 on who had jurisdiction. However, in its ruling the top court left the door open to federal-provincial co-operation.
Ontario and British Columbia started the ball rolling last year when they began work with Ottawa to develop complementary provincial and federal legislation governing capital markets.