Ian Lewis, the borough's director of early help and children's social care, and Sarah Baker, chair of the Croydon Safeguarding Children Board, stepped down following publication on Monday of a highly critical Ofsted report that found "weak managerial oversight at all levels".
The inspectorate's report rated both the authority and the safeguarding children board "inadequate".
The findings prompted the Department for Education to send in an improvement team to identify how best to fix the problems within Croydon's children's services and appoint Eleanor Brazil as children's services commissioner for the borough.
Following the resignations of Lewis and Baker, the council has drafted in Philip Segurola as interim director of early help and children's social care and Di Smith as interim chair of the safeguarding children board.
Segurola, a qualified social worker, had been working as Kent's director of specialist children's services and was a key figure in that council's recent improvements.
Smith is a former director of children's services in Brighton & Hove who has worked as a consultant with a number of authorities including Croydon, where she was interim executive director of children, young people and learning from 2010 to 2011.
Barbara Peacock, Croydon's director of people and its statutory director of children's services, remains in post.
The changes come amid claims from Croydon Council leader councillor Tony Newman to local media that the borough's cabinet members were led to believe the authority's children's services was improving.