The agency will work with the firm's personal injury practice to highlight cases involving medical negligence, workplace injury and accidents and illnesses abroad.
Irwin Mitchell has represented clients in high profile cases, such as Creutzfeldt-Jakob disease and the Hatfield rail disaster. It also continues to challenge legislation with landmark cases, including the breast cancer drug Herceptin.
The firm also champions causes which relate to its current cases such as those for victims of Mesothelioma and other asbestos-related diseases.
3 Monkeys will look to increase the profile of the company's work as part of the brief.
The 3 Monkeys team is led by head of consultancy Ali Gee, with support from three consultants, and reports into Irwin Mitchell head of media relations Mark Duffell.