Extraction of brackish groundwater in coastal aquifers is believed not only to mitigate the effects of seawater intrusion but also to reduce the desalination cost of the extracted water. However, evaluation of the groundwater quality in coastal aquifers is an essential initial step before determining the locations of brackish water extraction wells and extraction rates. Therefore, this paper presents spatial and temporal assessments of the groundwater quality in the coastal aquifer of Wadi Ham located in northeastern part of UAE. This assessment is considered as precursor for evaluation of the aquifer potentiality as source for water desalination. A total of 245 water samples from 26 different observation wells were collected over the period from 1989 to 2006 to assess the origin and quality of the groundwater in this coastal aquifer. It was found that saltwater intrusion from the Gulf of Oman was not the main source of brackish water in several parts of the aquifer prior to year 2000. However, results also show that more recently seawater intrusion has become the leading factor of water salinity in the aquifer especially near the coast. It was found that seawater intrusion extended about 8 km inland from the coast of the Gulf of Oman. (C) 2011 Elsevier B.V. All rights reserved.