They launched the initiative today at the headquarters of the United Nations in New York to tie in with International Volunteer Day.
The partnership means VSO and the Peace Corps will share support functions, such as training facilities, and agree not to overlap in countries where both organisations work.
The two will examine how they can collaborate further on volunteer projects concerned with education, health and HIV/Aids.
The partnership was first announced during President Barack Obama’s state visit to the UK in May.
The Peace Corps and VSO have worked together informally for more than a decade. For example, in Tanzania they collaborate to help teachers improve their English language skills and share materials, skills and accommodation for volunteers.
Marg Mayne, chief executive of VSO, said: "We’re quite different organisations in terms of our history, governance and the volunteers we work with, and this means each agency can complement the work of the other rather than overlap.
"This agreement builds on existing work to share skills, training and materials so we can be more effective in the benefit that we bring."
Aaron S Williams, director of the Peace Corps, said: "We will share best practices in programming and training, strengthening our united efforts to combat global poverty."