Daniel Britt was last seen over a week ago with his mother, Andria Britt, who authorities believed had fled to Washington State.
An Amber Alert said a court granted Daniel's father sole custody of him, after Andria Britt skipped a court date and failed to return the boy.
The alert also cited an "immediate risk of harm" to both Andria and Daniel Britt. The reason wasn't disclosed.
According to Island County Sheriff Mark Brown, two deputies peacefully took Andria Britt into custody Thursday evening. She had apparently been staying at a relative's house on Camano Island.
Daniel Britt was taken into protective custody and is expected to be reunited with is father in the coming days.
Andria Britt, has been charged with being a fugitive from justice and child snatching. She is being held in Island County Jail.
At a news conference Thursday night, Daniel's father, Sean Britt, said his son will be 7 years old on Jan. 24. Britt says he's "really relieved" Daniel is safe.