Political advertising especially outdoor types have since assumed prominent places in advertising plan during campaigns. However, there is a sharp division among researchers on the influence of these important advertising tools in our contemporary world. Therefore, the study was conducted to ascertain the role of billboard advertising in mobilising electorate during the 2023 general elections in Delta State. The study adopted the survey research method. A sample of 400 was taken from the population of 3,221,697 voters in the state and the researchers relied on questionnaire as instruments of data collection. The study saw a 97 percent response rate with the analysis based on 386 respondents' perceptions. Research findings revealed that there was massive use of billboard during the 2023 general elections in Delta State. It also revealed that the voters were exposed to billboard as a tool for political advert. Part of the findings of the study was that certain appeals were embedded in the political advertising to which the electorates were exposed with youth appeal being the most prominent. The researchers found that the exposure of electorate in Delta to billboard advertising did not influence their choice of candidates during the elections. The study concludes that billboard are important aspects of tools for 21st century political advertising but are not as powerful as assumed especially in respect of influence on voter behaviour and electoral decision during elections. The study, among others, recommends that there is the need to keep improving billboard advert to further make it a viable tool for political advertising in Nigeria.