In this study, bubble formation phenomena in the dispersion medium of magnetite nanoparticle in water during microwave irradiation were investigated. From the experimental results, it was found that under microwave treatment, the maximum bubble size was greatly influenced by the suspension density at a given temperature due to the distribution of microwave energy to the particles itself or the liquid-air interface of bubbles around the particle. Nanoparticles in the dispersion medium were also found to play a key role in achieving stable nucleation of bubbles on particles surface. Smaller bubble sizes were produced at higher suspension density. Microwave power also has a positive impact on the maximum bubble size especially at low suspension density. Moreover, particle material having dielectric constant property was also found to be an important factor for bubble size during microwave irradiation. From these results and findings, it is envisaged that bubble size can be controlled by the presence of nanoparticle and microwave irradiation.