The objectives of this research are to describe the effectiveness of employees internal communication, the internal communication barriers and the efforts to improve the effectiveness of employees internal communication in the Secretariat Sector of PT Pos Indonesia (Persero) Semarang Regional Office VI. This research is qualitative with descriptive analysis approach. The selecting of respondents used purposive sampling method. The methods in collecting data used were observation, interview and literature study. Primary data of this research obtained from three interviewees, they consisted of manager and two Secretariat Sector staffs. The results of this research shows the six factor created in order to support the internal communication of employees were credibility, content, clarity, capability and consistency, audience capability and channels of distribution. While the factor that less created to support employees internal communications was affinity relationships (context). So it can concluded that employees internal communication in the Secretariat Sector of PT Pos Indonesia (Persero) Semarang Regional Office VI run effectively. It could be seen from the factors that have been created to support the effectiveness of internal communication was more dominant than factors that have not been created yet. Moreover the barriers obstructing the process of employess internal communication in the Secretariat Sector of PT Pos Indonesia (Persero) Semarang Regional Office VI were differences of mindset, poor understanding in accepting a new job, a sense of unwillingness and cultural differences among employees. The efforts were being made to increase the effectiveness of employees internal communication were The efforts were being made to increase the effectiveness of employees internal communication were manager and employees tried to build open climate when working, considered information/instructions provided properly, eliminating cultures obstructed the effectiveness of communication. Suggestions proposed of this research are the employees of the Secretariat Sector of PT Pos Indonesia (Persero) Semarang Regional Office VI should cooperate in completing a job and hold a meeting or informal monthly meeting for reaching a better affinity relationship, employees should be positive thinking to eliminate the differences in mindset that often being a barrier in communication, provide direction and working implementation guide to improve the understanding of new job received, eliminate the aversion to build open communication between employees and understand the cultural differences between employees by holding seminar related to the cultural differences in organizations