The dolphin, which died in transit to Singapore last November, died of an acute bacterial infection, said Resorts World Sentosa (RWS) on its blog on Thursday.
The pacific bottlenose dolphin, was headed to RWS' new Marine Life Park.
RWS added that there was "no evidence on the origins of the infection" and that dolphin Wen Wen was given the all clear before being exported.
The remaining 24 dolphins are healthy and have completed their quarantine, it added.