Water shortages have led to measures such as the implementation of reclaimed water (RW) for irrigation in order to sustain agriculture. Waste water requires treatment to become a safe water resource for irrigation. This paper presents an analytical study on the use of RW for irrigation in the southeast of Spain, identifying its strengths and current limitations. It includes official data from 13 waste water treatment plants (WWTPs) belonging to two coastal irrigation districts in the Region of Murcia. The content of essential nutrients in some RWs might allow them to supply a large fraction of the fertilizers required by the crops, thus saving energy and reducing the cost of fertilization. However, the accumulation of chloride, sodium, and boron could damage soils and cause phytotoxicity to crops in the mid-term, reducing yields. Microbiological pollutants in the RW could also endanger human health and hence waste water treatment is required. In the selected WWTPs, all effluents met the minimum requirements established in Water Quality 2.3 by the Royal Decree 1620/2007 and also with the European Classes B and C proposed by COM 337. Blending RW and other water resources of better quality is recommended for the sustainable use of RW for irrigation.