After the Assembly Elections in 2006, CPI(M)-led Left Democratic Front (LDF) gained an absolute majority in the house. The State Committee and Polit Bureau of CPI(M) unanimously decided to make Achuthanandan the Chief Minister of Kerala. He took oath of office on 18 May 2006 as the twentieth Chief Minister of Kerala.
As a Chief Minister of the state of Kerala he has succeeded in the revival of several public sector units, measures to tackle price rises, reaching an agreement on the Smart City project in Kochi and the initiating firm action against encroachment of government land in the hill resort and tea plantation town of Munnar.