The triangular cord sign (TC sign) is a sensitive and specific tool in prompt diagnosis of extrahepatic biliary atresia. The objective of this study is to evaluate post-operative TC sign presence in outcome prediction of infants with biliary atresia after Kasai hepato-portoenterostomy 27 infants and children with biliary atresia underwent 122 ultrasound examinations using both 5 MHz and 7 MHz convex linear transducers in 33 months follow up. For all infants TC sign identification was included pre-operatively, ultrasound was done 2 weeks post-operatively then bimonthly for 3 months, monthly for 2 months and every 3 months thereafter. 14 (53.8%) had post-operative TC sign. Once post-operatively positive, it remained positive throughout the study. It did not reappear in an initially post-operatively TC sign negative infant. Those having post-operative TC sign had statistically worse outcomes (0 became anicteric, 2 improved, 7 had progressive disease and 6 died) than those with a negative TC sign (p = 0.04) (3 became anicteric, 5 improved, 2 progressed and 1 died). Presence of TC sign post-operatively correlated with measure of removal of all fibrous cone at porta-hepatis during portoenterostomy (p = 0.026). Post-portoenterostomy TC sign is associated with more morbidity and mortality; and reflects inadequate surgical technique.