This article deals with ballot order effect in preferential voting in general elections in Slovakia. Previous research in this field has primarily focused on countries whose elections are based either on single-member districts or on lists with fewer candidates. This article aims to analyze a case of a different nature. Slovakia uses a proportional representation list system with a single nationwide constituency where all 150 members of parliament are elected. Hence, most of the political parties create lists with a high number of candidates, which according to theory should enhance the influence of ballot ranking. Using data from Slovak general elections between 2006 and 2012 with a sample of 7,587 candidates, this study provides strong evidence of the impact of ballot order on the results of preferential voting. The analysis in this article shows the existence of both the primacy and recency effects, that is, a positive bias of voters towards candidates listed at both top and bottom positions on a list. What is more, the multilevel models used in this article demonstrate that support for top-ranked candidates significantly increases as the size of the list increases. For the bottom-listed candidates, this trend is rather the opposite. These findings represent a valuable contribution to the debate in this area as they provide insight into the role of ballot order in electoral systems that use lists composed of numerous candidates.