Mill Creek is a city in Snohomish County, Washington, United States. It is located between the cities of Everett and Lynnwood, approximately 20 mi northeast of Seattle. The city has a population of 18,244 as of the 2010 census, and is estimated to have over 20,000 residents as of 2018. The city lies along State Route 527 and North Creek, a tributary of the Sammamish River, on the east side of Interstate 5.