Raised in the Hunter Valley in NSW, Peter Cain had a 20 year career as a high school mathematics teacher, then as a teacher and principal in the non-government school sector. He was later drawn to the legal profession and completed a law degree in 2001, being admitted to the ACT Supreme Court Roll soon after.

Prior to his election to the ACT Legislative Assembly in October 2020, Peter managed the tax disputes section within ACT Treasury and served as Vice President of the ACT Law Society from September 2017 to September 2020. Peter was also Chair of the Government Law Committee from 2014 to late 2020.

Peter and his wife Claire have seven children and have lived in Evatt since 1997. Peter is focussed on being an advocate for the people of Ginninderra to ensure they receive the infrastructure and services they deserve.