Asthma is a common chronic disease that affects millions of people in the world. The most common signs and symptoms of asthma are cough, breathlessness, wheeze, chest tightness and respiratory rate. These signs and symptoms can’t be measured accurately since they consist of various types of uncertainties such as vagueness, imprecision, randomness, ignorance, incompleteness. Consequently, traditional disease suspicion, which is carried out by the physician, is unable to deliver accurate results. Hence, this paper presents the design, development and application of a decision support system to assess asthma suspicion under uncertainty. Belief Rule-Base Inference Methodology Using the Evidential Reasoning Approach (RIMER) was adopted to develop this expert system that is named as Belief Rule Based Expert System (BRBES). The system has the capability to handle various types of uncertainties both in knowledge representation and inference procedures. The knowledgebase of this system was constructed by taking account of real patient data and expert’s opinion. The practical case studies were used to validate this system. It was observed that the system generated results are more effective and reliable in terms of accuracy than the results generated by a manual system.