One of the intricate challenges in the sphere of international humanitarian law is «<direct participation of civilians in armed conflicts». Although humanitarian law speaks about the prohibition of direct participation of civilians in armed-conflicts, but does not provide any definition of that. In this paper, we try to clarify the nature and legal impacts of direct participation of civilians in armed conflicts. For this purpose we consider the necessary and the constituent elements of direct participation, causal hostile elements observed in the definition of direct participation, direct participation examples and broad interpretation of that on the one hand, and on the other hand application of human rights law and fundamental principles of humanitarian law on direct participation, detestable and non-detestable legal protection of civilians participating in armed conflicts. We conclude that in times of armed conflict any participation of civilians in hostilities with the purpose of injuring and destroying enemy combatants and equipment can be regarded as direct participation. This kind of participation is a crime itself and cause the civilian participating in hostilities to lose his/her protection and being liable for committing such crime.