Reinbeck is a city in Grundy County, Iowa, United States. The population was 1,664 at the 2010 census a five percent decrease from the population of 1,751 at the 2000 census. It is part of the Waterloo–Cedar Falls Metropolitan Statistical Area. Reinbeck resides in northeastern Iowa outside of the Waterloo-Cedar Falls area known as the Cedar Valley. Reinbeck is primarily an agricultural community that strives on the services of nearby larger cities like Cedar Falls.