Economic activity with respect to gambling and betting in Poland every year provides the State Treasury with significant revenues from taxes on gaming. This paper aims to characterize the mutual wager contract as a legal construction constituting the basis for participating in the mutual wager. Based on the provisions of the Gambling and Betting Act of 29 July 1992 and on the attainment of the doctrine and jurisdiction, the individual elements defining the contract are discussed and its characteristics compared to other aleatory contracts are presented. Attention is also drawn to the possibility of enforcing a claim for breaching the contract terms. The considerations expressed in the paper are based on the authors’ several-years experience in legal consultancy rendered to entrepreneurs on the Polish gambling market.