The Department of Adult and Juvenile Detention (a separate entity from the court) is responsible for the care and custody of youth who are detained in the juvenile detention facility. A youth may be detained following an arrest for allegedly committing an offense or on a warrant, pending trial, as part of a sentence, or as part of an order sanctioning the youth for violating the terms of probation. Non-offenders (truants, at-risk youth, children in need of services, or dependents) who violate a court order or are arrested on a warrant may also be detained. (See Detention Screening Criteria.)

While detained, the youth receives a medical assessment to determine whether the youth is in crisis and needs immediate medical or mental health intervention. The youth also receives an assessment to determine the youth's appropriate placement in detention and any special issues that may need to be addressed.

During the week, detained youth attend school. The Seattle School District provides regular and special education.

Detention staff work closely with probation staff to keep probation advised when a youth is detained.

Detention also manages programs providing alternatives to secure detention for those youth who require monitoring but do not need to be detained in a secure setting. These programs include electronic home monitoring, day and evening reporting, group care, and work crew.