Secure and sustainable supply of minerals is important for the stable development of a country’s economy, as well as the global economy. Poland’s economic performance—as a dynamically developing country—is also largely dependent on the availability of minerals and security of their supplies both from internal sources and form imports. In Poland, 42 key minerals—i.e., those of fundamental importance for the proper functioning of the economy and satisfying the living needs of the society—have been recently indicated. From among them, 19 key minerals have been recognized by authors as having a proven resource base in Poland and—on the other hand—having moderately- or strongly growing domestic consumption trends. An assessment of the mineral resource base for their production, a sufficiency of the resources of developed deposits, as well as possible means of undeveloped deposits safeguarding were analyzed and discussed. It was found that the long-term needs of the Polish industry can be satisfied only for some of them: coking coal, copper, and silver, as well as numerous industrial and construction minerals. Moreover, existence of a sufficient resource base and appropriate means of their safeguarding may potentially have a significant impact on Poland’s and Europe’s minerals security, in particular regarding several minerals for which Poland is an important supplier to the European market, i.e., coking coal, copper, silver, and elemental sulfur.