This paper examined the rerun election and electoral integrity in the 2018 Governorship election in Osun State. The paper utilized both primary and secondary sources of data collection. The primary data was collected through semi-structured interviews with twenty (20) purposively selected respondents including legal practitioners, electoral officers, political parties’ stalwarts, and academia. The respondents were selected based on their expertise on the subject matter and their involvement in the rerun election. The secondary data were sourced from relevant literature, textbooks, journals, election manuals and guidelines, magazines and library archives. The data collected were analyzed using content analysis. This paper concluded that the conduct of the 2018 rerun governorship election in Osun State lacks all the elements of a credible election and thus questions the integrity of the election. This is not unconnected with several factors, including political parties’ quest to control government at all costs, the nature of the zero-sum game of political parties, and voters’ mentality among others made the rerun election more controversial and thus affect its credibility. It is recommended among others that internal democracy rather than the imposition of candidates should be embraced among political parties in the selection of a party flagbearer.