Castroville is a city in Medina County, Texas, United States. Its population was 2,680 at the 2010 census. Prior to 1893, Castroville was the first county seat of Medina County. Castroville is known for its influential Alsatian-Texan architecture, people, and culture. Most Alsatians who came to Castroville spoke Alsatian (a dialect of German origin integrating Celtic, Yiddish, and French words). The Alsatian culture and language are still kept alive by the residents of Castroville.