This article aims to highlight the importance of the regulation of the official language not only for the state authorities but also for the individual as a guarantee of fulfillment of its constitutional rights and freedoms.The Polish Constitution of 1997 introduces in Article XXVII the principle of officialdom of Polish language, giving it for the first time since the nineteenth century such a strong legal protection. This principle was developed subsequently in The Polish Language Act in 1999 regulating the use of Polish language as a national language.The right to use Polish language in public and in private as the hallmark of citizenship should be protected by the State. Mother tongue as an element of national culture forms part of the national identity and therefore of the individual. The lack of obligation to know languages other than the official protects citizens from having to comply with European Law that has not been translated into Polish. The individual may also allege to the breach of Article XXVII of the Constitution when applied to the law that was interpreted in violation of language norms. Outside the protection conferred by Article XXVII of the Constitution there are now, as a rule, private law relations. It is due to the assignment to Polish language the status of an official language at the constitutional level and not of a national language. The introduction of the principle of officialdom in Article XXVII of the Constitution of the Polish language implies an obligation of the State to protect individuals that do not speak in that language. It is a condition for the realization of, inter alia, the right to justice. Article XXVII of the Constitution, the second sentence, as a guarantee regulation, confirms the inviolability of national minority rights resulting from ratified international agreements. Therefore, it correlates with the principle of the protection of national and ethnic minorities without giving the possibility to establish in Poland Polish language other than as the official language.