The aim of this article is to determine and assess the changes in the central functions of major Polish cities in the context of Poland’s 1999 administrative reform. This study covers a period of twenty-two years (1998–2019), which provides a solid perspective for evaluating the functional changes occurring within the current territorial division of the country. The conclusions indicate that the dynamics of changes in central functions in former provincial capitals differed from those in cities that retained this status. At the same time, it was found that the administrative reform sanctioned the scope and scale of earlier socio-economic dependencies in the present regional centers. The research results suggest that administrative reforms in Poland solidified existing socio-economic development paths in cities, but were not the sole catalyst for change. They point to a complex interaction of factors influencing urban evolution. By utilizing indicators that measure the centrality of cities in relation to their demographic potential, this research offers a quantitative assessment of the level of development of central functions, which is crucial for monitoring progress towards sustainable urbanization. By providing this information, this research also contributes to a broader discussion on the advancement and dynamics of sustainable urban development.