Recently, addition of nanofillers to insulating fluids to increase its breakdown voltage finds a great interest from researchers. Understanding the reasons of the increased breakdown voltage with addition of nanofillers at certain loadings to insulating fluids is of great importance. Hence, understanding how electric breakdown occurs in nanofluids can help researchers to select the more suitable nanofiller material, nanofiller particle size ....... etc. to be added to insulating fluids. Therefore, in this paper, a generalized electric breakdown mechanism of insulating nanofluids is presented. The generalized mechanism takes different parameters into consideration. These parameters are nanoparticle permittivity, nanoparticle size and insulating fluid temperature. To demonstrate the validity of the generalized breakdown mechanism, theoretical computations are carried out using finite element analysis. Also, breakdown experiments considering transformer oil are carried out considering different nanofiller materials, nanofiller sizes at different temperatures.