This paper presents an investigation of the effect of moisture content on the agglomeration and bulk density of coal. Growth mechanisms of agglomeration have been analysed based on microscopic observation and the results indicate that the relative roles of the growth mechanisms such as nucleation, coalescence and snowballing are dependent on the moisture content. It is shown that agglomeration occurs mainly to the moist nuclei coarse particles and the moist layering fine particles. Two types of porosity, namely intraporosity in an agglomerate and interporosity among the packed particles and agglomerates, are identified. The dependences of these two porosities and other properties of agglomerates, such as particle size distribution, moisture content and bulk density, on the moisture content are experimentally established. Analysis of these measured results suggests that the relationship between the bulk density and moisture content coal is dependent on the particle size distribution, particle (agglomerate) deformation and in particular, interparticle friction.