The Finnish airline plans to target travellers to Lapland as well as grow the number of passengers on its so-called "short cut" between Scotland and China.
The success of the route is also likely to increase Edinburgh Airport's hopes of winning a direct link to China.
Finnair will operate up to nine flights a week between Edinburgh and Helsinki this summer, up from three when it revived the link in 2016.
There will be up to three weekly flights in the winter.
Finnair boasts a shorter route to China and Japan than other carriers because of its rights to fly over Russia.
It acknowledged there was strong competition in Scotland from MiddIe Eastern airlines, but said passengers could save up to eight hours by flying via Helsinki rather than the Gulf.
The growth is part of the biggest expansion in Finnair's 95-year history, which will also include an extra daily flight from next winter between Helsinki and Rovaniemi,"the home of Santa Claus" in Finnish Lapland, on top of its existing links to Ivalo, Kittilä, Kuusamo there.
Finnair operated a summer route between Edinburgh and Helsinki in 2006 and 2007 before it was axed because of the recession.
The revived service in 2016 was originally planned for March to October, but was extended to early January from its first year.
The airline uses a 138-seat Airbus A319 aircraft on the route, with both business and economy class seats.
UK general manager Andrew Fish said VisitScotland and Edinburgh Airport had helped boost Chinese traffic, and the extended flights would cover the Chinese New Year, in February.
He said the route was evenly split between inbound and outbound passengers, with 20-50 per cent connecting with long-haul flights in Helsinki.
He said: "China is incredibly important to the route and there is quite a large Chinese student population in Scotland, while the Chinese also use Edinburgh as a gateway."
Edinburgh Airport chief executive Gordon Dewar has described the link as a "significant route for Scotland and one we have been working very hard to secure".
When it was announced, he predicted it would "open up Scotland to significant traffic from Russia, China, Japan and Finland itself.
He said: “I hope this is the beginning of Edinburgh Airport further strengthening Scotland’s links with these key global destinations.”
Mr Dewar said today: “We’re delighted that Finnair has extended this popular service between Edinburgh and Helsinki, offering passengers yet another destinationchoice the whole year round.
“Helsinki offers culture, architecture and design, but it also acts as a fantastic connection hub, opening up destinations in other countries such Russia, China and Japan.
"And that hub will clearly appeal to people from Scotland wishing to go see more of the world, and people from those parts of the world that want to come and discover Edinburgh and Scotland.”