Subject and purpose of work: The purpose of the article is to study the peculiarities of the development of environmental cross-border cooperation, as well as to determine the prospects and ways of deepening interregional Ukrainian-Polish cooperation in the environmental sphere. The relevant international environmental cooperation of the states contributes to the improvement of the environment and provides a defined level of environmental safety. The challenges of international economic greening as well as the needs in cooperation between the neighboring states indicate that studying of the ecological state on the cross-border territories is considered to be of great significance. Materials and methods: T he m ethods u sed a re t he a nalytical a nd d escriptive o nes b ased o n the critical literature review and an experiential reflective attitude on the key issues concerning the cross-border cooperation, ecological safety, and prospects of development of environmental cooperation. Results: The role of cross-border cooperation in ensuring environmental security was studied in the article. The strategic priorities of Ukrainian-Polish environmental cooperation were considered. As a result of the analysis of the current state and the achieved results, the prospects for further ecological cooperation between Ukraine and the Republic of Poland in the conditions of European integration were revealed. Conclusions: It is concluded that to assure the development of the Ukrainian-Polish cross-border environmental cooperation and to build the ecological safety system on the trans-frontier territories it is required at the regional level to establish partnership relationships in the environmental and economic sector; to intensify the environmental and economic international cooperation at various cross-border scales; to create a network of cross-border environmental information centers; to promote the environmental public education in the border regions of the neighboring states etc.