Nanoclay-reinforced agarose nanocomposite films with varying weight concentration ranging from 0 to 80% of nanoclay were prepared, and structurally and mechanically characterized. Structural characterization was carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was found that pre-exfoliated clay platelets were re-aggregated into particles (stacked platelets) during the composite preparation process. Each particle consists of approximately 11 clay platelets stacked together. The nanoclay particles were homogeneously dispersed within an agarose matrix. The clay particles were oriented with a slight preference of the stacked platelets being parallel to the composite film's surface within the low loading composite films. Mechanical properties of the nanocomposite films were measured by tensile, three-point bending and nanoindentation tests. Mechanical testing results show that nanoclays provide a significant enhancement to the tensile modulus and strength. For the 60% clay nanocomposite, its elastic modulus increases up to 21.4 GPa, which is five times higher than that of the agarose matrix. Based upon the structural characterization, a theoretical model has been developed to simulate the mechanical behaviour of the nanoclay-reinforced polymer composites.