This study reports on an outbreak of motile Aeromonas sep-ticemia (MAS) that caused significant mortalities in irides-cent shark catfish (Pangasius hypophthalmus) in bioflocsystems in the Punjab province of Pakistan. Clinical symp-toms observed on the affected fish included anal finhemorrhaging, mouth area bleeding, skin ulcerations, inter-stitial nephritis, and focal fusion of secondary lamellae.According to necropsy findings and a molecular phyloge-netic analysis based on gyrB gene sequences, the etiologicagent of the disease was identified as Aeromonas dhakensisAli.Pk01. The new isolate displayed resistance to multipleantibiotics such as ampicillin, cefuroxime sodium,meropenem, and penicillin, but remained susceptible to sev-eral antibiotics including amikacin, ceftazidime, chloram-phenicol, ciprofloxacin, levofloxacin, and oxytetracycline