The electronic and magnetic properties of graphene-like gallium nitride (g-GaN) with adsorbed H, B, C, N, O, and F atoms were investigated using spin-polarized first-principles calculations. We found that H, B, C, N, O, and F atoms can be chemisorbed on a g-GaN monolayer. The total magnetic moments of 1.0, 2.0, 1.0, and 1.0 mu(B) are founded in B-, C-, N-, and F-adsorbed g-GaN monolayers, respectively. In addition, a half-metallic state appears in the N- and F-adsorbed g-GaN, while a spin-polarized semiconducting state appears in other g-GaN monolayers after the adsorption of B or C. These findings demonstrate that the magnetic properties of g-GaN can be effectively tuned by the adsorption of non-metal atoms. In particular, the F-adsorbed system that exhibits a half-metallic state and high Curie temperature of 367 K has great potential for application in spintronics. (C) 2017 Elsevier B.V. All rights reserved.