The expansion entails a total investment of $1.19bn (€1bn), with the specialist bank already having offered $113.2m (€95m) in 2019.
Helsinki Airport, which was originally constructed in 1952 for the Summer Olympic Games hosted by Finland’s capital, is owned and operated by civil aviation company Finavia.
It has been undergoing work since 2014 to expand and upgrade the site.
In the fourth phase of the project, the existing terminal 2 is being modernised and expanded. It includes the expansion of check-in capacities and security checks as well as the improvement of baggage handling and claim.
Work also includes the construction of a new entrance with a timber roof. The work is expected to be completed by the end of this year.
KfW IPEX-Bank management board member Andreas Ufer said: “The financing of airports as central mobility hubs for entire regions is one of the cores of our business as a financier of infrastructure.
“Even though the aviation industry is currently heavily restricted due to the spread of Covid-19, we are anticipating demand to rise again after the pandemic has subsided. Then climate protection will come to the fore again.
“In this area, we have been particularly impressed by the early commitment of Helsinki Airport. We are delighted to be accompanying the airport, which is already considered carbon-neutral, on its path to becoming a zero-emission airport.”
In October last year, Finnair reached an agreement with Airpro and Aviator Finland for ground handling services at Helsinki Airport.