We examine the relationship between related party transactions (RPTs) and firm value and how this relationship is moderated by ownership concentration using a sample of 379 listed family and 151 non-family firms for the period 2007 to 2009. Ordinary Least Square Pooled Model as well as Fixed Effects Model panel data regressions are used in the data analysis. For family firms, we find that RPTs reduce firm value (proxied by Tobin’s Q and market-to-book value). Further, controlling shareholders’ ownership has a significant positive moderating effect on this relationship. However, for non-family firms, there is no significant evidence of firm value reduction and positive moderating effect respectively. We conclude that expropriation via RPTs is stronger in family firms compared to non-family firms. Additionally, an increase in controlling shareholders’ ownership helps mitigate this expropriation and this mitigating effect is stronger in family firms compared to non-family firms. The implications for the capital market regulator are discussed in this paper.