: Water losses occurring in water distribution systems (WDSs) are now considered as a serious problem, necessitating a robust and effective management strategy. Non-revenue water (NRW) data indicate that most cities in Gaza Strip, Palestine experience high NRW. In 2015, the average percentage of NRW in Gaza Strip was 39%. This figure resulted in major financial, supply, and pressure losses, as well as excessive energy consumption. The estimated annual volume of NRW in 2015 was in the order of 34 million m3 which is equivalent to American $ 16 million. Furthermore, NRW is a good indicative of water utility performance; high levels of NRW usually indicate a poorly managed water utility. This paper investigates the reasons why NRW is so high in many cities in Gaza Strip. Results of the study revealed that the lack of incentives for management units, the lack of awareness of citizens-users of the water service, apparent losses, the blockade on Gaza Strip, the wars on Gaza are the main causes.