Since Ukraine’s formal political regime has changed substantially several times over the last two decades, the country offers an ideal case to study the relationship between political regime dynamics and the political role of the oligarchs. Based on an original dataset covering all Ukrainian oligarchs and on case studies of different forms of political influence, this article shows that a core of oligarchs has remained stable throughout the period under study from 2000 to 2015 and that their strategies to exert political influence have remained largely unchanged. These strategies, based on informal manipulations, have clearly put the political opposition at a pronounced disadvantage. However, oligarchs are not the major power brokers in Ukrainian politics, as they have always sought accommodation with those having or gaining political power, i.e. the oligarchs do not determine who wins political power, but they act as catalysts for an ongoing change by giving additional support to the winning side. In such settings the major impact of regime dynamics on the political role of oligarchs has been in the degree of political rivalry. A higher degree of political rivalry leads to pluralism by default, which gives political parties, parliamentary deputies and mass media more freedom and is reflected in democracy rankings by better marks. However, as the oligarchs’ informal manipulations continue largely unchanged, such pluralism does not indicate a genuine commitment to democratic standards.