A device for mounting a light fixture structure to a ceiling grid. The device includes an anchor structure extending from the light fixture structure, with a pair of arm structures spaced to receive a ceiling grid segment therebetween at an anchor location on the ceiling grid adjacent a lower region of the ceiling grid. The arm structures have respective distal regions configured to be accessible from an upper region of the ceiling grid and a clamp structure configured to traverse laterally relative to the distal regions to couple with the respective distal end regions and thereafter to be transferable between a released position and a locked position. When in the locked position, the ceiling grid segment held between the anchor and clamp structures place the light fixture structure in the mounted position.