This article presents a constitutional perspective of collective labour agreements within the system of sources of law. The author particularly focuses on highlighting the constitutional-law nature of collective labour agreements. Additionally, the article points out doctrinal differences in the perception of the legal character of collective labor agreements. The author argues that collective labor agreements should be regarded as normative acts sui generis, which are not issued within the framework of legislative competence, but remain one of the fundamental institutions of collective labor law. According to the author, collective labour agreements do not constitute sources of law as defined in Chapter II of the Constitution, a position that is also sup ported by a substantial part of legal doctrine and the case law of the Supreme Court. Moreover, they do not have the character of being universally or internally binding, nor do they take the so-called “mixed” form. The publication also emphasizes that the compliance of collective labour agreements with the law should be determined by the competent common court, rather than the Constitutional Tribunal of Poland or the Supreme Administrative Court.