Civil society is positioned somewhere in the area between business, government, and private sector. As civil society organizations are not profit-oriented, they are often relying on the engagement of volunteers, i.e., workers who are not paid for their effort. Successful management of human resources in organizations that depends on volunteers’ work can prove even harder than managing employees’ work in business entities. Many factors influence someone’s work effort, productivity, and devotion far beyond technical conditions, so it is impossible to separate someone’s work from the rest of his/her personality traits. In civil society organizations, attracting, motivating, and keeping volunteers willing to conduct needed tasks and actively participate in the organization’s activities might be quite challenging. For this paper, a survey was conducted among 42 organizations of civil society units (CSUs) that use the help of volunteers to fulfill their activities. To analyze relative efficiency of the civil society units, appropriate input and output variables were selected, and analysis was conducted with non-parametric DEA method. It was decided to take 4 inputs and 2 outputs in the analysis. The obtained results show that 69% of 42 CSUs are relatively efficient, 31% relatively inefficient, and 26.19% below the average. The results of the analysis enabled the identification of efficient and inefficient units. The reference set was calculated for each inefficient unit to determine which inputs cause better performance output. The calculated projections can be useful to CSU’s managers and serve as a benchmark for detecting the source of inefficiency within their humanitarian organizations. They can also serve as guidelines for improving inputs and thus achieving higher levels of outputs, i.e., duration of volunteering and the number of volunteers.