Grundy Center is a city in Grundy County, Iowa, United States. The population was 2,706 at the 2010 census a 4.2% increase from 2,596 at the 2000 census. The United States Census Bureau estimated the population was 2,524 in 2009. It is the county seat of Grundy County. Grundy Center is part of the Waterloo–Cedar Falls Metropolitan Statistical Area.