No investigations have been performed on the rheological characteristics of cemented paste backfill (CPB) that contains nano-silica (nS) particles, although the addition of nS to CPB has been regarded as a promising approach to enhance the strength and strength gain rate of CPB at an early age. The present papers present the results of an experimental study on the impact of nano-silica (nS) on the theological characteristics of CPB. It is found that the nanoparticles considerably impact the theological properties of CPB, and thus alter its flow ability. The yield stress and viscosity of the CPB specimens incorporating nS are higher than that of the samples without nS. However, the magnitude of this effect is dependent on the binder type, curing time and water content. The findings described and discussed in this manuscript will support the development of the nano-CPB technology and its successful application in underground mine backfill operations. (C) 2020 Elsevier B.V. All rights reserved.