Ceramic membrane bioreactors (MBRs) have attracted a great deal of interest due to their robustness in the treatment of various kinds of wastewaters. So far, in situ chemical cleaning with sodium hypochlorite (NaClO) has been the most prevalent MBR cleaning method. This study showed that in situ NaClO cleaning in MBRs triggered a significant release of dissolved organic matter (DOM) from a sludge suspension, while the generated DOM could facilitate fouling development, especially irreversible fouling in a ceramic MBR. It was found that biopolymers with a molecular weight (MW) of >10 kDa and humic substances could be effectively rejected by the ceramic membranes. As such, the membrane fouling rate (dTMP/dt) of the supernatant from a NaClO-treated sludge suspension was closely related to the rejected levels of biopolymers and humic substances. However, hydrophobic DOM and low-MW organics (MW < 500 Da) could easily pass through the membranes, indicating an insignificant contribution to the observed membrane fouling. Consequently, this study verified the contributions of DOM released from a sludge suspension after in situ membrane cleaning with NaClO with respect to subsequent membrane fouling development in a ceramic MBR.