Massively multi-player online role-playing games (MMORPGs), such as World of Warcraft, have become very popular in recent years. These types of games typically feature rich and complex game environments, enabling more engaging game-play experiences. However, the complexity of the underlying game systems can also result in increased interface complexity, which may diminish player enjoyment - a major element of players' game experience. Players may customise their in-game interfaces to deal with this type of complexity and hence improve their performance, but the challenges associated with manual interface customisation may prevent some players from effectively personalising their own game interface. Players' behavioural models can be used to provide a means of determining potential player in-game behaviour, thus allowing for the automatic adaptation of game interfaces to better suit player needs. This thesis aims to determine whether player-modelled adaptive interfaces can improve players' game experience in MMORPGs. A survey of MMORPG players was conducted to determine which aspects of player experience may be impacted by interface modification. The findings of this study informed the development of an adaptive interface feedback system which aimed to provide players with relevant information, in order to improve their game experience. This prototype system was then evaluated, in order to determine the impact of the developed system on players' game experience.