To investigate the effect of natural convection on hydrate deposition in gas-filled deadlegs, a series of hydrate deposition experiments were conducted in a water-saturated gas system in a 1 in. deadleg, where water condensed on the cold pipewall gradually converted to hydrate deposits. The effect of natural convection was controlled by changing the pipewall temperature together with the system pressure while keeping the header temperature constant. In this work, natural convection was characterized by calculating the gas density difference between the top and the bottom of the vertical pipe and calculating the Rayleigh number. Based on the experimental results, the gas consumption in experiments and the thickness distribution, porosity, and dryness of the hydrate deposits under different natural convection intensities were analyzed and the effect of natural convection on hydrate deposition in gas-filled deadlegs was determined.