The Times of Gainesville reports that Jeffrey Simon Hubbard entered the not guilty plea Tuesday to all charges, including first-degree homicide by vessel.
The boy, Kile Glover, was the son of Usher's ex-wife, Tameka Raymond.
Authorities say Kile and his father, Ryan Glover, were vacationing at Lake Lanier when Hubbard crashed a personal watercraft into the boy's raft July 6. Kile died at a hospital July 21.
Hubbard, whose lawyer Jeff Talley entered the plea on his behalf, also pleaded not guilty to charges of reckless operation of a vessel, unlawful operation of a personal watercraft, boat traffic violation and serious injury by vessel.