A3 problem solving is improvement process that applies lean thinking to present report in a structured manner. This process improvement methodology identifies and eliminates waste to satisfy organization’s potential goals such as improving productivity, satisfy customers, reduce the operation costs, and support the decision-making. The problem solving is a key ability in manufacturing environment. An ineffective decision making can affect productivity, the lead time and manufacturing costs. This paper used case study to present A3 thinking approach by developing a very simple and structured report for improvement process. The results of case study show the developed A3 report, which goes from the identification of the problem, determination of current situation of the process, identification cause of the problem, determine how to tackle the problem, evaluation of improvement and determination of the effectiveness of the process. The result has also showed that the cycle time of line reduced from 180 minutes to 172 minutes and 25 seconds. The reduction was due to identification and elimination of non-added values. Application of A3 problem solving process has demonstrated the applicability and paybacks of the methodology in manufacturing industry.