High moisture content of indoor air can have serious health implications for occupants. Conventionally, dehumidification in buildings is realised by mechanical vapour compression, while desiccant materials with a high attraction for water vapour show promise for environmentally-friendly indoor air conditioning without overcooling or reheating problems. For dehumidification, solid desiccant materials rely on the adsorption of vapour molecules onto the surface to retain moisture, which is different from the liquid desiccant materials which absorb water molecules into the solution. Solid desiccant materials are of great importance to the solid desiccant-based system because the material characteristics affects the system performance markedly. Vermiculite as a natural and safe material has a long history of use in gardening and commercial horticultural, having great absorptive capabilities because of the concertina-like structure. However, few studies have been presented regarding its application for built environment and dehumidification performance for indoor humidity control. Composite desiccant materials are receiving wide attention owing to their improved property for dehumidification and regeneration. In this study, two vermiculite-based composite desiccants have been synthesised, with vermiculite used as a host matrix and CaCl2, MgSO4 as hygroscopic salts. Experimental tests have been conducted under various operating conditions using an advanced environmental chamber to simulate a hot and humid indoor environment. The experimental results demonstrate the feasibility of using vermiculite-based desiccants for indoor humidity control. Compared with silica gel-CaCl2, improved dehumidification performance is achieved by the vermiculite-based composite desiccants.