Johnston has lived and worked in Wellington with roles at a variety of galleries and cultural institutions, including the
Adam Art Gallery,
City Gallery Wellington, and from 2012 to 2018 was the director of the
Dowse Art Museum after roles at the
National Library of New Zealand and
Boost New Media where she worked in communications and web roles. In 2019, Johnston became the youngest chief executive to head
The Museum of New Zealand Te Papa Tongarewa where in 2024 she introduced a $35 entry fee for international visitors. She is also a board member of Arts Wellington and the Wellington Performing Arts Trust and the immediate past chair of the umbrella group Museums Aotearoa. ==Awards==