Planning of the Taipei Mass Rapid Transit (MRT) System began in 1975. Following the Executive Yuan's approval of the initial Taipei MRT network in April 1986, the Preparatory Office of DORTS was set up on June 27 that year. A reorganization of the Office brought about the Department's formal establishment on February 23, 1987, as a task-force unit under the jurisdiction of Taipei City Government.
Charged with the important responsibility of implementing Taipei MRT projects, at its inception DORTS consisted of five divisions, one center, and six offices with a total staff of 562. To meet the requirements of new tasks, such as joint development, quality assurance, and passenger transport service, DORTS received approval from the Executive Yuan on March 22, 1989, to add two new units – the 6th Division and the Quality Assurance (QA) Center, bringing the staff quota up to 740. Later, in conjunction with the establishment of the Taipei Rapid Transit Corporation Preparatory Office, DORTS transferred 188 employees from its Division 5 & 6 to the Taipei Rapid Transit Corporation (TRTC). Accordingly, the organizational structure of DORTS was reshuffled to reflect these changes.
On April 8, 1991, the Executive Yuan gave its approval for DORTS to make further organizational changes. At that time, DORTS headquarters consisted of 14 units with a staff of 604. Later, after the initial network was completed and commercial service began, as development of additional lines continued fewer lines were under simultaneous construction. DORTS was then reorganized to adapt to MRT construction requirements. Taipei City Government reduced DORTS’ staff quota to 546 on April 24, 2003. In addition, five district project offices (East, North, South, Central, and Systemwide E&M) were established to carry out MRT construction. The Systemwide E&M Project Office has a staff quota of 133, while each of the other four project offices has a staff quota of 104 employees.