This paper provides an estimation of exhaust emissions released by passenger ferries at the port-level. The methodology is based on the “full bottom-up” approach and starts by evaluating the fuel con-sumed by marine diesel engines on the basis of its individual port-activities (manoeuvring, berthing and hoteling). Specific air emissions are estimated as regards to the different propulsion sources: main engine, auxiliary engines, thrusters and boilers. The Port of Barcelona was selected as the site at which to perform the analysis, in which 25 passenger ferries operating in the Mediterranean Sea were monitored. Real-time data from the Automatic Identification System (AIS), factor emissions from engine certificates, engine loads during port time, and vessel characteristics from IHS- Sea web database were also collected for the analysis. The research findings will improve our understanding of local pollution at port-cities and help to derive appropriate measures to improve air quality.