The internal moisture content of cotton fibers is a major impediment in the accurate measurement of strength. NIR spectra have been used to generate correction factors to be applied to the measured strength. Partial least squares (PLS) was used to find the combination of four wavelengths that gave the best predictions. Application of these correction factors reduces the variation in strength measured at different relative humidities (RH) to the variation in measuring repetitively the strength at the same humidity level.