As a company that has been established since 1963, PT ARV management is currently making efforts to change and develop in order to maintain its business field. When an organization wants to make a transformation or change to improve its performance, the organization first needs to assess its current performance. This study aims to help PT ARV obtain an overview of the current condition of the organization and to design appropriate interventions based on the results of the organizational diagnosis. Using the Six Box Model as the method of diagnosing the organization, this research was carried out by combining the qualitative and quantitative methods in its research design, also known as mix-method design. In addition to interview, observation, and documentation, this study also used a questionnaire adapted from the Organizational Diagnosis Questionnaire (ODQ) developed by Preziosi as a data collection method, while for data analysis techniques using descriptive analysis. The result of the study diagnosed that PT ARV had problems in structure, relationship, reward, and helpful mechanism whereas the rest of the dimensions indicated no problem in the organization. The relationship between work units is known as the dimension that is most considered not effective by respondents. Therefore, the intervention design provided is intergroup team building training to improve the quality of relations among work units. Improved relations between work units are expected to improve the quality of social system that balance the technical system in the input-output transformation process in PT ARV.