Transformation products (TPs) of pharmaceuticals have raised great concerns due to the extensive detection and potentially higher concentration and toxicity than parents. However, the related knowledge on TPs of pharmaceuticals in wastewater were limited. To fill this gap, suspect screening workflow was developed to identify TPs from 28 pharmaceuticals in 12 wastewater treatment plants (WWTPs) located in Yangtze River Delta region of China. Based on the developed suspect lists included structural information and predicted retention time for 1643 TPs, 67 TPs were successfully identified at confidence levels of ≥3 and 61.12 % of them originated from non-steroidal anti-inflammatory drugs. Subsequently, target screening revealed that 4‑hydroxy-diclofenac, diclofenac-benzoic acid, N-demethylation tramadol, 10,11-dihydro-10-dihydroxycarbamazepine and 10,11-dihydro-10,11-epoxycarbamazepine exhibited high concentration up to μg/L in WWTPs. Comparatively, the cumulative concentration of TPs was higher than parents of pharmaceuticals in effluent of WWTPs. In addition, the predicted results revealed that 29.85 %, 82.09 % and 19.91 % TPs have higher toxicity, persistence and bioaccumulation than parents. Furthermore, diclofenac-benzoic acid and 10,11-dihydro-10,11-epoxycarbamazepine exhibited higher eco-risks than their corresponding parents and N-demethylation tramadol was found to be with moderated eco-risks in effluent of WWTRPs. Collectively, the present study provides holistic information on TPs for 28 pharmaceuticals in wastewater and highlights the importance for TPs of pharmaceuticals in WWTPs from the aspect of concentration, toxicity and eco-risks. In the future, not only parents, but also TPs of pharmaceuticals should be effectively managed and attenuated in wastewater.