The study, to be released during this week's meeting of the United Nations Commission on the Status of Women, called for proportional representation of women at every level of multilateral organizations, from field offices to headquarters, as well as in secretariats and governing bodies.
"But I also believe that women bring this combination of leadership, wisdom and empathy, and sometimes, an even greater understanding of what is happening in the world."
Since 1945, the 33 institutions studied have had 382 leaders, but only 47 were women, the report showed.
And despite recent progress, only one-third of the institutions are currently headed by women.
GWL Voices said it would release a more extensive version of the report in September that would also look at the senior management teams and governing bodies of the 33 institutions.