Despite the fact that researchers have been studying electrical conductivity for about fifteen years, there are very few publications dedicated to this topic. This is in contrast to the large number of publications on the study of thermal conductivity and viscosity of nanofluids. This chapter will present the main data of the current research. The electrical conductivity of nanofluids with conventional spherical particles and CNTs will be discussed separately. The chapter begins with a description of the theoretical background on electrical conductivity of coarse dispersed fluids. The mechanisms of electrical conductivity in nanofluids with both conventional particles and CNTs are analyzed separately.