Utilization of mineralized fossil water (MFW), as a by-product of oil production is a special environmental problem in oil and gas areas. In Ukraine the annual production of mineralized fossil water together with oil is estimated at about 20 million tons. Taking into account that MFW is an aby-product of oil production, they are usually placed in waste disposal sites and can contaminate environment. It was determined that toxicological properties of mineralized fossil water have not been studied so far. There is the need for study of toxicological features of the MFW which will allow to determine its hazard class and to develop some measures for safe usage of this drug for making the agriculture more ecological. Thus, in the work we have made the assessment of ecotoxicological properties of MFW as an environmentally safe substitute for agrochemicals. It was established that MFW is referred to low-toxic compounds. LD50 for oral introduction of the compound in the bodies of white female rats is more than 21,000 mg/kg, female mice - 31,000 mg/kg, male mice - more than 20,000 mg/kg; when applied to the skin of rats – more than 8000 mg/kg. The value of LD50 when applied to the inhalation routes of entry for female rats is more than 5000 mg/kg. It was justified that by oral route of entry and skin penetration the MFWs belong to the IV class of danger, and by inhalation route of entry – to III class. It was also determined that MFW does not have an irritating effect on the skin and mucous membranes of the eyes. There is also no sensitizing effect on the body of guinea pigs. Studies have shown that the cumulative properties of MFW are weakly represented. The accumulation coefficient is greater than 5. At a dose of 4260 mg/kg MFW has cardiotoxic effect, it affects the process of erythropoiesis and increases filtration and excretory function of the kidneys. Ineffective dose for rats in a subchronic experiment is 2130 mg/kg. These results of ecotoxicological study of MFW make it possible to confirm that its usage is safe in the agricultural system, especially as environmentally friendly organo-mineral fertilizer, herbicide, and fungicide.