McGuirk will remain at the museum and head up its climate crisis-focussed Future Observatory programme.
"Johanna Agerman Ross is hugely respected across the cultural and design sectors. She is a writer, teacher, magazine founder, consultant and curator," said Design Museum director and CEO Tim Marlow.
"Her experience ranges from museums and academia to publishing and journalism, wide-ranging but rooted in the understanding, exploration and mediation of design," he continued.
"She has all the attributes to be an outstanding chief curator at the Design Museum and I'm very much looking forward to working with her."
In 2011, Agerman Ross founded the quarterly design journal Disegno. She had previously edited the architecture and design magazine Icon, which was launched by Dezeen's founder Marcus Fairs. She continues to oversee Disegno as its director.
Since 2016, Agerman Ross has worked at the V&A museum in London as its curator of 20th-century and contemporary furniture and 20th-century product design.
At the V&A, Agerman Ross's achievements have included co-curating the museum's permanent gallery Design 1900-Now alongside Corinna Gardner and leading the initiative Make Good: Rethinking Materials, which is an annual symposium that explores the use of natural and renewable materials in design and architecture.
The writer and curator also volunteers for the charity Young Women's Trust, assisting women seeking work with CV writing and job application letters.
The Design Museum is currently showing Chinese artist Ai Weiwei's first design-focussed exhibition, Making Sense.
The portrait is by Chris Tang.