PLAN was founded in 1937 in England as the Foster Parents Scheme for Children in Spain by English journalist John Langdon-Davies. He and Eric Muggeridge, an English social worker, conceived the idea of providing financial support and hostels for children orphaned or made refugees by the Spanish Civil War.

As European economies began to recover in the post-war years and individual countries became able to assume responsibility for their own needy children, PLAN began to phase out its European operations and looked to lend assistance to undeveloped countries where the needs of children were the result of causes other than war. To reflect this change in focus, the organization changed its name once again from Foster Parents Plan for War Children, Inc. to Foster Parents Plan International, Inc. and began to establish field offices and programs in Latin America, South America, Africa, and Asia.

The first South American field office was established in Bogota, Colombia in 1962. The Bogota program was rapidly followed by programs throughout South America and Latin America in the 1960s. Programs in Africa and Asia followed in the 1970s and 1980s. Some programs were also terminated during this period, either due to improving economic conditions, as in Hong Kong, or deteriorating political conditions, as in Ethiopia, Nicaragua, Liberia, and Vietnam.

As PLAN expanded it also changed its focus from a child welfare organization to a community development organization. Though PLAN continued to emphasize the welfare of individual children, it did so in the context of a community development approach that sought to strengthen families and communities in order that they may better support their children's needs.

With the change in emphasis came a change in organizational structure. By the early 1970s, it had become apparent that PLAN's relatively informal administrative structure was no longer adequate to meet the needs of a rapidly growing organization. This realization resulted in the establishment of PLAN International in 1973 as the administrative arm of Foster Parents Plan International, Inc. with its headquarters in Warwick, Rhode Island. The International Executive Director, responsible to the International Board of Directors, was to manage the operations of PLAN with the assistance and support of a senior management group. The national organizations in Australia, Belgium, Canada, Germany, Japan, the Netherlands, the United Kingdom, and the United States enjoyed relative autonomy in raising funds from individual foster parents and corporations. These funds were then funneled through International Headquarters to the various field offices.

PLAN continued to grow throughout the 1970s and 1980s and its organizational structure continued to evolve as well. In response to complaints from field directors that PLAN management had become too centralized and unresponsive to the needs of the field offices, International Headquarters began to decentralize its management structure. Beginning in 1987, PLAN established a series of regional offices in order to move the operational decision making process as close as possible to the programs and field offices. By 1992 the process was completed and six regional offices oversaw the management of program activities in the field offices responsible to them.

The evolution of PLAN' s administrative structure continued into the 1990s. After twenty years in Rhode Island, the International Executive Board, at the recommendation of new International Executive Director Max van der Schalk, agreed to move its International Headquarters to England. The move, approved in 1993, was completed in late 1994.