but it is apparent that the impact of diversification still generates much debate given the mixed findings (Palich et al., 2000;Volkov & Smith, 2015). Some studies revealed that implementing a diversification strategy can adversely the performance affect (Zhou, 2011;Hashai, 2015;Gyan, 2017), which is in contrast to other studies that pinpointed how diversification strategies actually can improve the company performance (Kuppuswamy & Villalonga, 2016;Chan, Bany-Ariffin, and Nasir, 2019).One of the factors causing the differing research results is the use of variables that moderate the relationship between diversification and company performance (de Andrés, Fuente, & Velasco, 2017). Among these factors is corporate governance, which includes the level of supervision and chief executive officer (CEO) performance (Jara-Bertin, 2015). In particular, diversification can cause a company's organizational structure to expand, which leads to higher information asymmetry. Such an issue poses great difficulty for coordination and supervision (Bushman, Chen, Engel, & Smith, 2004; Rodríguez-Pérez & Van Hemmen, 2010), decreasing the company's performance.The increasingly complex coordination in companies with a broader organizational structure makes it vital to establish an effective coordina-This study examined the effect of diversification strategies on firm performance and the extent to which the chief executive officer (CEO) commitment moderates this relationship. The effect of diversification on firm performance was analyzed in a sample with both above-average and below-average diversification levels. The sample consisted of 76 manufacturing companies listed on the Indonesia Stock Exchange (IDX) from 2007 to 2018, which were analyzed using panel data regression with a balanced panel. Tobin's Q was utilized to measure firm performance, compounded with three measures of diversification strategies: entropy index, Herfindahl index, and the number of segments. The results show that diversification leads to lower firm performance, whereas CEO commitment eliminates the negative influence of diversification on company performance in all measurement models (i.e., entropy, Herfindahl index, and the number of segments). Accordingly, the negative effect of diversification strategies and consistent CEO commitment were observed among the samples with high and low diversification levels.