The present invention is a modular deck system with height adjustable leg assemblies. The deck modules each have a top panel, a support frame, and a leg receptacle. The leg assemblies include a base foot, an adjustment bolt and a leg bracket with four legs extending perpendicularly from a bracket plate. A height adjustment bolt is fixed to the base of the leg assembly and extends perpendicularly from the base through an aperture in the bracket plate. The deck modules are placed adjacent to each other, side-by-side and end-to-end in the desired layout, then secured with the leg assemblies. Leveling of the deck modules is achieved through rotation of the adjustment bolts.