This paper examines the role of aggressiveness on performance of firms on the Nigerian Stock Exchange. The paper is designed to look at the role of aggressiveness on performance of firms on the Nigerian Stock Exchange. The paper took critical interest in the contents of a number of studies which concluded that among Nigerian managers, lack of innovation and pro-activeness, aggressiveness, aversion to risk-taking, which are critical factors for growth of SMEs, were found to be high in 2007. The target population is 176 firms listed in the Nigerian Stock Exchange with financial returns as at August, 2014. Out of the population, a sample of 60 firms was taken. Methods of statistical analyses include mean, standard deviation, and Pooled, Random and Fixed regression models based on the preferences suggested by the Hausman specification test results. The results of panel analysis of the relationship between Entrepreneurial Orientation dimension – aggressiveness, and performance of firms listed in the Nigerian Stock Exchange, with returns on assets and returns on equity as proxy showed a positive relationship between aggressiveness and returns on assets and aggressiveness and returns on equity. This result negated a study conducted in 2007 in Nigeria on 88 SMEs earlier mentioned. But, it also confirms the outcome of a study carried out among Kenya’s manufacturing firms operating under the EAC in 2012, which showed that there existed a positive relationship between entrepreneurial orientation adoption and firm performance. Aggressiveness was found to have positive relationships with both returns on assets, and returns on equity. The implication of this study results is that, in Nigeria, entrepreneurial orientation has been widely adopted and practised, and aggressiveness exhibited a positive relationship with both returns on assets and returns on equity as it was found in Kenya.