Outside of Shantou, Mackenzie founded the Taiwan Mission on behalf of the Presbyterian Church and was invited to speak at missionary conferences in an array of cities that included Philadelphia, Shanghai, and Bristol.

She made numerous contributions to the mission that complemented her husband's work, such as her important role in the construction of a boarding school for girls in 1873.

[6] After the completion of the main hospital, Mackenzie began to establish out-stations in surrounding areas that brought more patients in contact with the mission, thereby exposing more Chinese to the gospel.

The Shantou mission was constructed in such a way that it was built around a “well-equipped center” from which missionaries would “work outwards to surrounding counties,” thereby prompting Mackenzie to venture into unfamiliar areas that lacked requisite medical infrastructure.

In 1860, along with Carstairs Douglas, a fellow medical missionary of Scottish origin, Mackenzie identified the suitability of Taiwan as a mission field.

[8] Mackenzie would periodically serve the Presbyterian Church of England in a non-medical capacity in regions outside his designated mission location of Shantou.

The Counsel lasted from September 23 to October 3, 1880, and welcomed any church organized on Presbyterian principles, featuring delegates from a variety of nations across the world, such as Australia and India.

Frederick Foster Gough and gave his speech “On the Duty of the Foreign Residents Aiding in the Evangelization of China—and the best means of doing so.”[13] Mackenzie died while in Shantou on December 26, 1899.

Mackenzie was admired for his willingness to venture away from the center of the mission and out into surrounding areas, where he would provide medical assistance and spread the gospel to previously overlooked communities.

His founding of the Taiwan Mission and translation of the scriptures into Shantou dialect were also accomplishments that would have a meaningful impact on future generations of Chinese.