Evaluation and selection of the appropriate supplier is complicated and time consuming decision making process for companies. Selection of inappropriate supplier leds to higher cost and it influences negatively business process of companies in competitive environment. In this paper, fuzzy-TOPSIS method, considering combination of quantitative and qualitative evaluation criteria, is presented to select appropriate supplier under uncertain environment. The proposed model is applied to the electronic signature purchasing process of a firm that operates in banking sector in Turkey. Quality, purchasing costs, additional costs (maintenance, training, and update costs etc.), security level, compatibility with existing IT infrastructure, after-sales support, and technical competence are selected for supplier selection process in accordance with a detailed literature review and experts' opinions.