Kyle Lewis Dunn was last seen leaving his home in Scotton, near Knaresborough, at around 6pm today.
A police spokesman said: "Officers are concerned about Kyle’s welfare and want to find him to make sure he is alright.
"He was last seen wearing the distinctive grey jumper he is pictured in and a black body warmer."
The search is focusing on the Harrogate and Knaresborough area.
Anyone who thinks they may have seen Kyle, or knows his whereabouts, is urged to contact North Yorkshire Police immediately on 101, select option 1 and quote reference 12170204947.