Silk is a culturally important textile, found in many artefacts of historic significance including clothing, upholstery, banners and decorations. However, it is a fragile material and is prone to deterioration via a variety of mechanisms, particularly after certain historically common processing methods such as bleaching and weighting. Therefore it is important to be able to accurately characterise the material in order to inform the most appropriate strategies for conservation, display and storage. NIR spectroscopy allows the non-invasive, in situ investigation of these textiles, and when combined with chemometric (multivariate) analysis to draw correlations with data obtained by other methods, can provide a wide range of valuable information. Using these techniques, we have demonstrated that it is possible to gain information about the physical state and integrity of silk; although this is complicated by the range of degradative reactions which silk can undergo, it is possible to draw correlations between NIR spectra and mechanical properties derived from tensile testing. This will enable potential conservation treatments to be directed at those objects and areas in greatest need of intervention, and may also highlight aspects which may warrant additional investigation via other methods.