The yield strength dependence on strain rate was studied for molybdenum-alloy nanofibers with varying initialﾠdislocationﾠdensity at three different pre-strain levels.ﾠIn-situﾠtensile experiments at three displacement rates were carried out in aﾠscanning electron microscope.ﾠYield strength and its scatter decreased as a function of the pre-strain level for different displacement rates. Aﾠstatistical modelﾠwas used to analyze the results, and a negative strain rate dependence was inferred from the yield experiments. This finding suggests the need for theoretical investigations since classical models such as dynamic strain aging may have limitations at such nanoscales.