It is the first client for the agency's new health and wellness arm and the first time the charity has employed a PR agency.
3 Monkeys is tasked with providing strategic PR and comms support for the charity, which helps children who are not expected to live past the age of 19, and offers guidance and support to their families, as well as home care.
Dr Martin Godfrey, managing director of 3 Monkeys' health and wellness arm, will lead the account, reporting to Juliette Gillard, head of comms and marketing at the charity.
3 Monkeys aims to position Shooting Star CHASE as a global centre of excellence in palliative care for children and elevate awareness to help secure the £23,000 of funding required each day for the charity to operate.
Gillard said: 'Children's hospice care can have many misconceptions and we are keen to start building awareness and understanding of the vital work we do.'
Separately, 3 Monkeys has won the account for internet security software maker Trend Micro from Octopus.