Dense non-aqueous phase liquids (DNAPLs) are organic pollutants that are insoluble in, and denser than, water, and have been discovered in aquifers underlying populated areas across the globe. The movement of DNAPLs in coastal aquifers, where tides and seawater create complicated flow paths, has received little attention. This study examines the movement of three different DNAPLs: TCE, CB and HFE, which differ in density and viscosity. Two-dimensional (cross-sectional) representations of coastal aquifers are adopted in both physical (sand tank) experiments and numerical modeling, which included the effects of both the seawater wedge and tides. The observations of DNAPLs responding to tides are the first physical experiments to do so. The results show that in isotropic and homogeneous aquifers, DNAPLs change the shape of the seawater wedge upon contact with it, pushing the toe seaward. The seawater wedge significantly expanded the area and increased the residual amounts of DNAPL trapped in the aquifer. The tide promoted seaward migration of the DNAPLs, tending to flush the DNAPL mass from the aquifer, although this had little effect on the volume of the aquifer containing mixtures of ambient groundwater and DNAPL. DNAPLs with lower density were more significantly affected by seawater and tides. The findings from this investigation show for the first time the opposing effects of seawater and tides on DNAPL migration in coastal aquifers.