•The order of entry has a U-shaped influence on firm performance in online IT service markets.•This nonlinear entry timing effect holds with different performance metrics.•Market growth moderates this nonlinear entry timing effect, but market concentration does not. Market entry timing, which is also known as entry order, has been proven to significantly influence firm performance under different circumstances. The inherent nature of the online context and IT services complicates the relationship between entry timing and firm performance. This study empirically examined entry timing effects in the online IT service market and the moderating effects of market characteristics. With a unique dataset collected from an online IT service platform, we discovered that entry timing has a U-shaped effect on firm performance: both early and late entry resulted in superior performance to that of intermediate entry. We also revealed that market growth moderates these curvilinear entry timing effects, with both early and late entrants benefiting more in high-growth markets than they did in low-growth markets. The results of this research enrich the relevant entry timing theories by examining entry timing effects in emerging marketplaces and the contingencies of markets.