Townsend, who was appointed to the top job in 2015, is expected to leave the ministry on December 1.
She will take up a regional post at the United Nations Educational, Scientific and Cultural Organisation (UNESCO) office in Samoa.
Townsend joined the Ministry of Education in 2003 and initially held the position of science advisor before rising through the ranks to senior positions of director of policy and planning and executive director.
She brought with her a wealth of knowledge and experience in education, including a master’s degree in International Educational Policy and Planning, and a Master’s degree in Science.
Last week the Cook Islands Public Service advertised Townsend’s role alongside the secretary positions for the Ministry of Health and the Ministry of Internal Affairs.
Health secretary Elizabeth Iro also resigned recently after she was appointed as the chief nursing officer at the World Health Organisation (WHO).
And earlier this year Paul Allsworth was appointed the acting Ministry of Internal Affairs secretary after former secretary Bredina Drollett accepted the position of acting chief of staff at the Office of the Prime Minister.
Public Service Commissioner Russell Thomas said he was hoping to fill the positions before the Christmas break.
He said each position carried a three-year term, with an opportunity to continue for another term pending good performance.
In the advertisement, the Cook Islands Public Service said it was on a journey to excellence to achieve the national vision, “to enjoy the highest quality of life consistent with the aspirations of our people, and in harmony with our culture and environment”.
The job description said the secretary was accountable for ensuring public service excellence through the effective and efficient delivery of the ministry’s functions and government policies.
The deadline for applications is 4pm, on December 1. Late applications will not be considered, the Public Service Commission says.