RCMP say they made the arrest with the help of Edmonton's police tactical unit at an apartment in the city's northwest Tuesday night.
The youth is one of three teenagers charged in the manslaughter of Ethan Yellowbird from the Samson Cree First Nation in Hobbema last July.
The boy was sleeping in his bed when a bullet fired from outside his bedroom wall struck him in the head.
The other two teens had already been picked up by police and appeared in court Tuesday.
Police say the accused were 13, 16 and 17 at the time of the shooting and are all from the Hobbema area.
Chief Marvin Yellowbird, who had adopted Ethan as his spiritual grandchild, has said he hopes band members will keep talking with police so more arrests are made in unsolved crimes.
The crime-troubled reserve is one of four in the Hobbema area. The First Nation has struggled with gang violence for years.
Last week, Samson Cree members voted in favour of giving their leaders the authority to evict suspected troublemakers. Ethan's shooting was cited as one of the reasons the referendum was held.