Othello is a city in Adams County, Washington, United States. The population was 8,549 at the 2020 census, a 16 percent increase fro…Othello is a city in Adams County, Washington, United States. The population was 8,549 at the 2020 census, a 16 percent increase from 2010. It is located in the heart of the Columbia Basin Project, approximately 100 miles southwest of Spokane. The city is 25 miles south of Interstate 90 in Moses Lake and is connected by State Route 17 and State Route 26.