This study presents in situ visualization of the emulsification/demulsification of asphaltene-stabilized water-in-oil emulsions using microfluidic devices. Monodisperse water-in-oil emulsions were generated using a T-junction, and droplet coalescence was analyzed further upstream of the collision chamber. The state of aggregation of asphaltenes contained in the model oil was found to strongly affect the stability of the emulsions. The aqueous phases used in this study contained either surfactant (C12-15E7) or microemulsion with and without demulsifiers. Different demulsifiers and their concentrations were observed to dramatically affect the coalescence rate. The dilatational surface viscoelasticity properties were also measured using a pendant drop tensiometer. Surprisingly, no correlation was found between the dilatational surface viscoelasticity response and the coalescence rate of the water-in-oil emulsions.