[4] The origins of YIT can be traced back to 1912, when Sweden's General Engineering Company (Swedish: Allmänna Ingeniörsbyrån) established a subsidiary in Finland, initially to operate in the water supply sector.

[6] The firm's field of operation was gradually broadened over the following decades, but it was not until the 1970s that the company moved beyond the civil engineering sector into construction of buildings (including residential property) and industrial works.

[7] In September 1987, Yleinen Insinööritoimisto merged with rival Finnish contractor Perusyhtymä Oy, creating YIT-Yhtymä (YIT Corporation).

[7] Primatel, the network construction and maintenance arm of the telecommunications firm Sonera, was added in 2002,[12] and a year later the building systems concerns of ABB in Russia and the Nordic and Baltic regions were acquired, further increasing YIT's presence in the service sector.

[19] This growth is also reflected in the scope of YIT's business: long-term servicing and maintenance contracts for items such as steam boilers, piping, heating, plumbing and electricity networks and water treatment plants now account for over a quarter of annual revenues.

[20] The Construction Services division, building homes, water and waste treatment plants and infrastructure ranging from railway stations to golf courses remains the group's largest source of revenue as of the end of 2006.

[30][31][32][33] In July 2014 according to leading Finnish newspaper Helsingin Sanomat YIT is more connected than previously expected in the bribery investigation of Helsinki construction during 2003–2011.