The contact angle of particles attached to fluid interfaces plays a key role in many scientific and technological aspects of particle-laden layers. In spite of the recognized importance, the laws that govern this property are still poorly understood. The main problem associated with the study of this property is that multiple variables are involved in the wetting process of particles by fluid interfaces. Such variables are associated with the chemical nature of both the particles and the fluid phases, and with the particle’s size. Understanding of the different aspects controlling the contact angle of particles is a physico-chemical challenge, and is very important because of the many technological aspects in which particle laden interfaces are involved. This review discusses the current status and the aspects to be dealt with in the near future in the study of the contact angle of particles attached to fluid interfaces. Display omitted