The objective of this thesis is to study in order to obtain the effective coordination and communication systems to reduce the error producing in production department for a sample plastic packaging company. From the research, the coordination and communication systems are set up. The systems that set up consist of formal and informal coordination and communication. The systems use organization structure as a guideline for coordination and communication process. So the organization structure is changed to be suitable for the effective systems. Job description is created. The standard activity flow and document flow is set up. Document is revised and added up. From all changed the coordination and communication can processes in systematic pattern. It helps to reduce conflict and error in the organization that come from misunderstanding in coordination and communication. The workers can understand their role, duty and responsibility in coordination and communication in the organization. The workers understand and have guideline for process, instruction and direction of coordination and communication systems by using standard activity flow and document flow. The documents can be used as a media to transfer the information in the pattern that everyone can understand. Production manager encourages and guides the supervisors, leaders and workers to use informal coordination and communication. Small and large group meeting is set and encouraged to set with formal and informal form. With informal coordination and communication, the positive attitude and positive feedback happen. It helps to reduce error producing in production. Error producing problem comes from poor coordination and communication. After implemented coordination and communication systems the results show that error producing reduces from 13.3% to 3.7%. The details are that excesses producing reduce to 3.36% from 10.27, short producing reduce to 0.09% from 0.67, and incorrect producing reduce to 0.27% from 2.34%.