The fire at the single-story home was reported around 10:15 p.m.
Firefighters fought the blaze defensively and the fire was under control within 30 minutes, Marysville fire marshal Tom Maloney said.
The people inside fled the home after hearing breaking glass.
The injured man was flown to Harborview Medical Center. His condition and age were not available Friday morning.
Damage was estimated at $220,000.
The Snohomish County Chapter of the American Red Cross is assisting the family.
More than 28 firefighters battled the blaze, with mutual aid provided by Snohomish County Fire District 15 at Tulalip Bay.
The Snohomish County Fire Marshal's Office determined the fire was accidental and caused by misplaced smoking materials, Maloney said.
Maloney said it is important for people to remember to check their smoke alarms regularly and practice their emergency plan.
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