The aim of this research was to investigate the causes of time overrun in the telecommunication projects in Zambia. To achieve this goal a multi-mode descriptive study was adopted by using both qualitative and quantitative approaches. A detailed literature review was done and sixteen purposively sampled project managers and subject matter experts (SME) were interviewed to obtain expert judgement on the factors affecting time management. The thirty-four factors identified from the interviews were categorised into five generic causes using the fishbone diagram framework: Process, Management, Equipment, People and Environmental factors. A questionnaire containing the thirty-four identified delay factors was distributed to the rest of the professionals from network operators, equipment vendors, contractors, telecommunication infrastructure support companies, involved in telecommunication projects with a response rate of seventy-eight percent obtained. From the results, the eight highest ranked factors were identified with the highest frequency of occurrence and impact on the schedule. Most of the interviewed experts pointed to poor planning as the main cause of project schedule overrun, affecting subsequent project phases. Based on the fishbone framework, it was found that process-related factors were the major contributors to project delays. These results highlight the need for telecommunication network operators to improve the time management processes, considering the emerging trends of outsourced model of operations