In the Netherlands, charitable behavior for international development purposes is subject to important changes. Whereas established development organizations suffer from a declining support base, private development initiatives (PDIs) that execute concrete, small-scale projects within direct personalized aid networks can count on increasing enthusiasm from individual donors of money and time. We investigate to what extent cost-benefit evaluations of volunteers (supply side) and characteristics of PDIs (demand side) affect the time allocation for volunteering in these organizations. The study is based on a survey among 661 volunteers active in Dutch PDIs. PDI volunteers face time and budget restrictions, partly due to their position on the (paid) labor market. Volunteers who are skeptical toward established development organizations increase voluntary time investment in PDIs. Corroborating the proximity hypothesis, volunteers perceiving a smaller distance to beneficiaries, spend more volunteering hours in PDIs. Volunteers also spend more hours volunteering for PDIs with larger budgets and more staff.