Rotational moulding of plastics is primarily used for the manufacture of hollow products. The predominant material used worldwide in this industry is polyethylene of various densities, most commonly in powder form. Previous studies of reinforcement materials in rotational moulding often report problems with agglomerations or inward migration of the filler. A shortcoming of rotational moulding is the difficulty of adding fillers due to the process’ nature of moulding at only atmospheric pressure despite being in a closed mould. In spite of the advances in machine adaptations and mould configurations to apply internal pressure, this study focusses mainly on non-pressurized composite production. Halloysite is a natural nano-size mineral clay, occurring in different morphologies, such as tubular, platy, and spheroidal. It has an aluminol and a siloxane surface, which present different degrees of reactivity. Due the low surface charges – exfoliation or intercalation is not necessary -, halloysite is easier to process compared to other clay fillers and achieve good particle dispersion, which renders it to be a potentially suitable candidate for reinforcing rotationally moulded products. Additionally, halloysite showed to improve the thermal stability of LLDPE, which is very important as rotational moulding is usually performed close to degradation temperature. In this study, nanoparticle-reinforced composites containing halloysite with medium density or high density polyethylene are produced by rotational moulding. The influence of halloysite on the processability - melting temperature, melt flow index and internal mould temperature -, and mechanical properties - tensile, flexural and impact -, is investigated. Keywords: Rotational moulding, halloysite, medium density polyethylene, high density polyethylene, nanoparticle-reinforced composite.