There is a widespread view that the impact of leverage on firm performance is ambiguous, with some studies finding a negative relationship (see Chen, 2004; Tian and Zeitun, 2007; Salawu, 2007) and others reporting either a positive or no significant relationship (see Azeez, 2015; Brick and Ravid, 1985). Theoretically, the divergence in previous studies can be partly explained by competing theories such as the signalling theory which posits that debt, in the presence of asymmetric information, should be positively related to firm profit performance, and the agency costs or pecking order theory which predicts a negative relationship between leverage and firm performance resulting from the agency costs between firm owners and lenders. Empirically, one plausible explanation for this ambiguity, in our view, may be the failure of existing empirical studies to model the contingent role that the size of a firm plays in the relationship between leverage and firm performance. If firm size impacts firm performance and the relationship between leverage and firm performance remains a subject of discussion, then firm size should provide some explanation for the ambiguous relationship between leverage and firm performance. This is the hypothesis advanced in this paper and forms the basis on which our empirical analysis is built. To reiterate, we ask whether the size of a firm helps to better understand and explain the ambiguous relationship between leverage and firm performance that has been documented in previous studies. As a by-product of this question, we determine whether there exists an optimal level of firm size at which leverage does not diminish firm performance. In addressing the main question posed in this paper, we employ the concept of threshold analysis, à la Hansen (1999) which is most suitable when nonlinearities between financial variables are to be explored. The concept of threshold regression modelling has a wide variety of applications in economics and finance. Our motivation to draw on the framework of threshold analysis stems from our main objective – we wish to determine whether the relationship between leverage and firm performance depends on firm size. That is, whether size is an advantage for firms and whether large-sized firms in Nigeria are better able to reap the benefits of leverage than their smaller counterparts. We have focused on Nigeria’s listed firms because several studies (see Akinlo and Asaolu, 2012; Jeleel and Olayiwola, 2017; Olokoyo, 2013; Patrick and Ogebe, 2013, among others) have mostly concluded that debt is generally bad for firms in the real sectors as it is responsible for the weakening firm performance that has been observed across these firms over the years. This has led many listed firms across the different real sectors of Nigeria’s economy to favour corporate governance policies and business strategies that promote less debt relative to other funding sources. The danger with such policies in a frontier emerging market such as Nigeria is that it stifles the opportunity for organic growth of firms, especially in the likely instances where other funding sources are either very limited or completely absent. Furthermore, these studies on the leverage-performance nexus in Nigeria have an important drawback. They did not consider the contingent role that other factors such as firm size might play in the leverage-performance nexus, and little is known about whether the size of a firm could be a game changer regarding the empirical relationship between leverage and firm performance. .