The purpose of this research is to understand the organizational cultures of Non-governmental Development Organizations (NGDOs) in order to identify their resistances to working with the gender approach and the best strategies to deal with this issue. My central question was: Is there a gendered conception and practice of power in the Peruvian NGDO culture? I used qualitative analysis, with three approaches for data collection: phenomenology, ethnography, and focus group discussion. I applied eleven phenomenological interviews to staff and managers of four mixed Peruvian NGDOs. I made ethnographic observations of the four organizations, and I carried out one focus group discussion with three other NGDO staff. The research demonstrates that there is a gendered conception and practice of power in the NGDO's culture. This conception is so ingrained, that it is accepted as the universal rule in most organizations, even by women managers. However, despite the gender-blind discourse of women and men managers and very similar official structures and written policies in the organizations, I found the initial composition of the organization the most crucial element in defining gender and power in the organizations. Organizations that started with both men and women in the workplace have challenged some practices and assumptions but these changes are not yet recognized in the management discourses and practices as a contribution in developing a more human work environment. In organizations that were initially male staffed and which had become mixed, men had developed a silent resistance to women's integration into the organization, in subtle and not very subtle ways, and this resistance expresses highly gender-biased assumptions regarding men and women as producers, reproducers and sexual beings. Highlighting these issues allows NGDO staff and managers to enhance their own capacity of creative and critical thinking and find their own solutions to their own problems. The proposed strategy for change includes special work regarding how women and men see each other as human beings, concentrated on cultural and symbolical change, through a participatory and long-term process.