Abandoned mining sites are largely responsible for the release of heavy metals into water systems. This study assessed heavy metals in the water collected from the mine sumps and bore-wells of an abandoned copper mine in Lasail, northern Oman. Other physiochemical parameters of the water were also evaluated. The waters were extremely acidic with very high electrical conductivity. Aluminium (Al), boron (B), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn) and zinc (Zn) were in very high concentrations, well above the limits recommended by Oman and World Health Organisation (WHO) standards. The principal component analysis (PCA) explained 93% of the variability. The impact of mining on the water quality of Lasail area is presented and remediation measures are recommended.