Pumice deposits, which are found in several areas of the North Island, NZ, are lightweight, highly crushable and compressible, making them problematic from an engineering and construction viewpoint. In this paper, the results of a research programme undertaken to investigate the properties of pumice sand at grain-size level in order to understand its macro-response are presented. SEM and X-ray CT images were acquired to visualize and quantify the particle shape characteristics and distribution of voids within the grains. Single particle crushing tests were performed to characterize the particle strength. Geotechnical laboratory tests, including bender element tests, dynamic deformation tests and monotonic/cyclic undrained triaxial tests, were conducted on pumice sand specimens and the results were compared with those obtained from hard-grained sands. The results indicate that due to the complex surface shape and low crushing strength of pumice, interlocking effect appeared to be significant, resulting in higher mobilised peak frictional angle and higher liquefaction resistance when compared with hard-grained sands. These results confirmed that the micro-level characteristics of the pumice particles have significant effect on their macro-level response.