Mr Purdey was said to be leaving the firm immediately “to pursue new challenges”.
He joined Intelliflo in November 2014, at which time Mr Eatock took on the role as executive chairman.
Mr Eatock said: “Hamish has done a fantastic job over the last five years with Intelliflo, a period in which we have grown the business to 35% market share, with almost 23,000 users.
“I’d like to thank Hamish for his enormous contribution and wish him well in his future endeavours.”
Mr Purdey said: “I have thoroughly enjoyed my time with Intelliflo, I am very proud of everything we have achieved, including the seamless integration of business critical systems, the development of the Personal Finance Portal (PFP) and the ability to deliver access to new technology for advisers, such as Open Banking.
“I am confident I am leaving the business well positioned for continued success and growth.”
On returning to the role of CEO, in addition to his existing responsibilities of executive chairman, Mr Eatocksaid: “I am delighted to be returning to the role of CEO at an enormously exciting timing for the organisation.
“Having worked closely with Hamish for the last five years we will be able to effect a seamless transfer of responsibilities and ensure continuity for staff and clients alike.”
Intelliflo has enjoyed rapid growth since its inception in 2004.
Its business management system, Intelligent Office (iO), has 22,700 users from 2,350 firms with assets under advice of £395bn.