Like micro-silica (MS), nano-silica (NS) can also be considered as a supplementary cementitious material for production of high-performance mortar and concrete. To investigate the influence of MS and NS on the fresh properties of mortar or the mortar phase of concrete, an experimental program encompassing mortar mixes with various water, cement, MS and NS contents was launched for undergoing flowability, cohesiveness and adhesiveness measurements. It was found that the NS added, albeit at much smaller dosage, has greater effects than the MS added on the fresh properties of mortar. More importantly, NS has negative effects on flowability, but positive effects on cohesiveness and adhesiveness. These results suggest that by enhancing the cohesiveness and adhesiveness, the addition of NS in conjunction with MS is a promising method for producing mortar with high adhesiveness requirement, as reflected by the results of the newly developed stone rod adhesion test.DOI: http://dx.doi.org/10.5755/j01.ms.23.4.16632