The production and use of polymer nanofibre assemblies prepared by electrospinning is now widespread. It is known that the tensile properties of electrospun polymer fibres can be different to those of bulk polymers. Here, we report a general method for measuring the tensile properties of individual electrospun nanofibres that employs a commercial atomic force microscope. Methods for preparing samples, force calibration and calculation of tensile stress and strain are described along with error estimation. By appropriate choice of AFM cantilever, it is shown that the tensile stress-strain curves can be measured for glassy, rubbery and gel polymer nanofibres. Testing can be in air or fluid and to strains of 300%. Example results illustrate the usefulness of the technique with the observation of high ductility in normally brittle glassy polymers such as polystyrene, and unusually large hysteresis in thermoplastic elastomer nanofibres. These observations provide new insights into the structure and mechanical behaviour of nanoscale polymeric materials. 2013 Elsevier Ltd. All rights reserved.