This article examines the intricate relationship between publicity andsecrecy in the Warsaw Sejm of the Kingdom of Poland in the context ofits sub-imperial status under Russian suzerainty. It focuses chiefly onthe three conventions of the body, held in 1820, 1825, and 1830–31.The 1820 Sejm saw significant public engagement, marked byintense debates and the emergence of new political ideas. However,this surge in public interest was met with dissatisfaction by EmperorAlexander I, prompting the imposition of secrecy during the 1825Sejm. While the 1825 session witnessed resignations among manyrepresentatives, certain Polish statesmen advocated for the principleof secrecy. In contrast, during the 1830 Sejm, members sought toleverage secrecy for their own strategic purposes. The NovemberUprising (1830–31) gave rise to a revolutionary Sejm that embracedpublicity, attracting large audiences and sparking public debate.However, this period also saw the rise of extra-parliamentary actors,such as the Patriotic Society and influential periodicals, whichquestioned the Sejm’s legitimacy. This article concludes that in thissub-imperial context both publicity and secrecy had paradoxicaleffects, fostering a politicization that could either empower orundermine the representative assembly. Consequently, the casesanalysed herein challenge the conventional narrative of publicityleading to democratization, and secrecy diminishing politicallegitimacy of representative assemblies.