Mockridge took the helm of News International, publisher of The Sun and The Times, following the phone-hacking scandal surrounding the now defunct News Of The World (NOTW) and the subsequent departure of Rebekah Wade.
He is being replaced by BSkyB COO Mike Darcey.
Former Times and current Wall Street Journal (WSJ) managing editor Robert Thomson has secured the CEO role at the planned demerged company, which will continue to be called News Corp. The entertainment company will be called Fox Group and contains, among other divisions, Twentieth Century Fox.
The proposed News Corp company is likely to see properties such as the Times, WSJ and Dow Jones working more closely together.
Mockridge is a long serving News Corp executive and became News International CEO in July 2011. Under his watch the newspaper group has focused on developing commercial opportunities and launched the Sun on Sunday publication to replace NOTW.
Darcey takes up the news International role before new proposals for UK press regulation are developed based on the details of the Leveson report.