Mill Creek is a city in Snohomish County, Washington, United States. It is located between the cities of Everett and Lynnwood, approximately 20 miles northeast of Seattle. The city has a population of 20,926 as of the 2020 census. The city lies along State Route 527 and North Creek, a tributary of the Sammamish River, on the east side of Interstate 5. The city is one of the wealthiest suburbs in the Seattle metropolitan area and was originally a planned community conceived in the 1970s.