Waldo is a village in Waldo Township, Marion County, Ohio, United States. The population was 338 at the 2010 census.here were 157 housing units at an average density of 241.5 per square mile (93.2/km 2). The racial makeup of the village was 96.4% White, 0.3% African American, 0.9% Asian, and 2.4% from two or more races. Hispanic or Latino of any race were 1.2% of the population.