Background: The Corniche is the main road that runs along Alexandria's coastline. Since 1998, certain developmental activities have been undertaken along this road, aiming at widening it in order to overcome the traffic congestion and to compensate for the erosion of some beaches. Objectives: to assess the impact of such developmental activities on the Mediterranean Sea water quality. Methods: During the period from July 2011 to March 2012, a single water sample was collected monthly during summer and winter seasons from four chosen beaches. Sea water samples were subjected to physical, chemical and microbiological examination. Wilcoxon signed-rank test was used to determine the variation in sea water quality following Corniche Road Widening Project. Besides, an assessment of the quality of sea water in the selected beaches was carried out by comparing different measured characteristics with national and/or international standards. Results: Results of the study revealed that Corniche Road Widening Project did not cause any statistically significant difference in any physicochemical characteristic of sea water in both Sidi-Bishr and Cleopatra beaches. As for Stanly beach, dissolved oxygen (DO) and nitrate increased significantly (to 7.7 ml O2/L and 3.9μmole/L respectively) and, in Shatby, DO increased while turbidity and alkalinity decreased significantly. They were found to be 7.7 ml O2/L, 0.045 NTU, and 1.6mEq/L respectively. Concerning the biological characteristics of sea water, there was a statistically significant difference in four parameters measured in Shatby beach. With respect to sea water quality, beaches under study were all complying with Egyptian guidelines, WHO and USEPA as regards physicochemical properties. Concerning microbiological quality, all samples were complying with WHO and EPA levels for enterococci except in August. Conclusion: The study recommends the use of best management practices for all construction projects with possible impacts on water bodies, and emphasizes the importance of environmental impact assessment studies and continuous monitoring of sea water quality for public health protection.