The humanitarian sector is in need to prioritize its human resources. Inadequate recruitment processes, aid workers that enter the field unprepared, failed interrelationships and team dissatisfaction leads to poorer work quality, poorer health, and a high employee turnover that are costly for the field, and negative on the side of accountability to the beneficiaries of aid. In order to address these problems the study is investigating the use of a personality type system tool developed by the researcher, the 4mpt-system (4 major personality types-system),that tentatively is constructed as a tool to be applied within human resources in the humanitarian sector to access individual preferences and character traits that would facilitate in addressing the issues mentioned above. The data is gathered via in-depth semi-structured interviews of 7 informants working in the international humanitarian sector. The first objective is to study the reliability and validity of the 4mpt-system. The second objective is to study what information that could be accessed via the 4mpt-system tool from the 7 informants participating in the study. The result of the study would demonstrate that all of the informants could be assigned to a specific temperament type via a qualitative data analyze method designed from the 4mpt-system and that the temperaments affected the informants to a large extent (from motivations and skills to organisational preferences and personal belief systems). Further, the answers of the informants matched the theoretical definitions of the traits assigned to the temperament types by Keirsey (1998) and Fisher (2009), which was a positive indication for a good validity of the 4mpt-system. By verifying the similarity between the answers of informants assigned to the same temperament type, validity was further confirmed. The results of the study supported the reliability and validity of the 4mpt -system. The type of information that could be accessed via the 4mpt-system in the study was among other the motivation for beginning in the humanitarian field, work task preferences, professional skills, problem-solving approaches, decision making processes, likes and dislikes with work and work tasks, organisational structure preference, preference for working directly in the field or working from the office, and general outlooks and personal belief systems.