In twin screw wet granulation process, the binding excipients could be added in two ways: premixed with powder materials before granulation or dissolved in water as a solution. In this paper, the feasibility of using micronized lactose as a solid binder excipient in twin screw granulation process was examined. Different proportions of micronized lactose were mixed with lactose and microcrystalline cellulose (MCC) powder before granulation, respectively. As a comparison, hydroxypropyl cellulose (HPC) was prepared in solid and liquid phase (i.e. premixed with powder and dissolved as solution respectively). Granulation was carried out to investigate the binding potential by studying the effect of micronized lactose and HPC on the granules properties such as size, shape and surface structure. Due to its small size, micronized lactose was proven to be an ideal alternative as a solid binding excipient to provide strong bonds and produce granules with improved granule size distributions. Furthermore, the binding capacity of micronized lactose was also examined on the compact powder bed where the contact angle, nucleus hardness and surface structure were studied. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.