PurposePakistan has experienced financial liberalization with rapid ups and downs in economic growth due to domestic issues during the last 2 decades. Motivated by inconclusive and conflicting time-driven findings about the performance of the business groups, this study examines the performance of business groups in Pakistan for a relatively long period from 2003 to 2018.Design/methodology/approachThe study uses 3,821 firm-year observations from non-financial firms listed on the Pakistan Stock Exchange (PSX). For the estimation, pooled ordinary least squares (OLS) with industry- and year fixed effects and two-step system generalized methods of moments (GMM) are used.FindingsThe study finds that group-affiliated firms outperform independent firms in accounting performance, while underperform in market performance. The outperformance is mainly driven by medium-sized business groups, while underperformance is driven by small and large business groups. Further, the study documents that the underperformance in terms of market performance of firms affiliated with small and large groups is greater before the economic downturn, while outperformance in terms of the accounting measure of firms affiliated with medium-sized groups is greater during the economic downturn. These findings support our time-driven concerns. Overall, the authors' findings are consistent with institutional and transaction cost theories.Practical implicationsBusiness groups are important channels to reduce market inefficiencies. Business groups may enhance the affiliated firms' resources and resistance capacity through active utilization of the internal capital market, specifically when market conditions are not ideal for affiliates. However, effective utilization of internal capital markets depends on group size. Therefore, investors should deliberate on the size of business groups and diversification within business groups.Originality/valueThe authors extend the literature by providing fresh evidence related to the performance of business groups in the Pakistani context while accounting for the role of the size of business groups.