The 25-year-old will now miss his side's matches against the Tennessee Titans, the Denver Broncos, the Miami Dolphins and the New England Patriots as a result of the ban.
The Chiefs said on their official website: "This morning the NFL notified the team of Donald Stephenson's four-game suspension.
"Obviously losing Donald is disappointing, but we are in full compliance with the league's policy. We will have no further comment on the situation."
Stephenson has played 32 games since arriving in the NFL in 2012.