During the tumultuous period surrounding the Chinese Communist Revolution of 1949, Chinese children wrote thousands of letters to foreign “foster parents” as part of a humanitarian fundraising strategy known as the “adoption plan” for international child sponsorship. Under the adoption plan, private citizens around the world “adopted” Chinese children by paying for them to live in orphanages in China while building personal relationships through the exchange photographs, gifts, and translated letters that used familial terms address. This paper uses the case study of the Foster Parents Plan for War Children China Branch (“PLAN China Branch”) to examine how Chinese child welfare workers mobilized the emotional and economic ties between children and their foster parents to secure material and ideological support for the revolution abroad. Under the rubric of “people’s diplomacy,” the PLAN China Branch channeled money to “progressive” child welfare institutions while encouraging children to write their foreign foster parents with intimate narratives of how they had suffered under the American-allied Nationalist regime and were now thriving under the Communists. Based on 490 extant letters sent by Chinese children to their foster parents through the PLAN China Branch, it analyzes how the adoption plan became a centerpiece of broader efforts to transform humanitarian practices inherited from the Republican period to meet the new ideological and material needs of the Chinese Communist revolution.