The Equality Trust was launched in 2009 by Bill Kerry, Richard Wilkinson and Kate Pickett. The idea for the Trust was developed from 2007, after Kate and Richard secured a publishing deal for The Spirit Level: Why More Equal Societies Almost Always Do Better (the original hardback title) and Bill recognised the potential for a campaign based on their evidence.

In 2008 the Trust was awarded funding by the Joseph Rowntree Charitable Trust  which enabled the founders to commission a website and employ their first member of staff. The Equality Trust's launch coincided with publication of The Spirit Level on 5th March 2009.

In November 2009, a new campaign called One Society was set up by The Equality Trust and the Network for Social Change. One Society's main focus was promoting policies that would take us towards a more equal society - as well as responding to political developments relating to top pay and income inequality. In 2013, One Society was fully merged into the Trust.

The Trust obtained charitable status in May 2015 and in 2018 joined forces with Pay Compare, the UK pay ratio campaign. 

The Trust continues to be funded through a combination of charitable trusts and support from many generous individuals and organisations for which we are very grateful.