USAID defines private voluntary organizations as tax-exempt, non-profit organizations working in, or intending to become engaged in, international development activities. These organizations receive some portion of their annual revenue from the private sector (demonstrating their private nature) and voluntary contributions of money, staff time, or in-kind support from the general public (demonstrating their voluntary nature).

Many Non-governmental organizations (NGOs) working in international development and humanitarian aid prefer the term to NGO. NGOs typically include any private or nonprofit entity that is formed or organized independently from any national or local governmental entity. These can include for-profit firms, academic degree-granting institutions, universities and colleges, labor institutions, foundations, private voluntary organizations, and cooperative development organizations.