In recent years, healthcare systems have been involved in a number of different changes, ranging from technological to normative ones, all asking for increased efficiency. Since patient safety related problems are major concern for healthcare institutions around the world, so the healthcare institutions have to pointed out the main reasons of different kinds of medical errors and to find out the ways for reducing their frequency. In this paper we use a new fuzzy fault tree approach and the two widely used defuzzification methods has been presented for patient safety risk modelling in healthcare. This approach applies fault-tree, trapezoidal-triangular interval–valued fuzzy numbers, - cut, and the signed distance operations to obtain fuzzy failure probability of the system. The effectiveness of the developed approach is illustrated with a problem taken from literature related to healthcare. Computed results have been compared with results obtained from two defuzzification methods.