Ship performance in actual seas represents the true performance of the ship throughout the service life and is affected by the combination of various conditions i.e. environments, loading patterns and ship conditions. Environmental conditions of wind, wave, swell and ocean current are chaotic and stochastic in nature. Loading condition may vary in draft, trim and motions in each voyage. Ship condition is susceptible to hull and propeller fouled over years. This paper provides insight into the service performance of Liquefied Natural Gas Carriers (LNGC) in actual seas derived from post-mortem on years of voyage's noon report collections. Evaluation method of service performance will be proposed and benefits that can be gained from such analysis will be discussed. © 2014 Penerbit UTM Press. All rights reserved.