Both in-plane and through-thickness linear viscoelastic properties of the single-wall carbon nanotubes (SWNT)/polyelectrolyte multilayer nanocomposite film were characterized using nanoindentation. The SWNT nanocomposite films with a SWNT loading of 4.7% by weight was made by layer-by-layer assembly (LBL). The viscoelastic functions of materials were measured using two methods: (1) the direct differentiation method from the load-displacement data; and (2) the material parameter extraction method by fitting the analytical load-displacement relation to nanoindentation data. Results from both methods agree well. The in-plane Young's moduli of the films were also measured from small-scale tensile tests; the results agree well with nanoindentation data. This investigation indicates that the in-plane and through-thickness linear viscoelastic properties are almost identical for a SWNT nanocomposite made by LBL technique, despite the preferred orientation of the SWNT in a nanocomposite film. (c) 2005 Elsevier B.V. All rights reserved.