Tubular anodic alumina membranes, containing self-ordered and circular pores below 100 nm, were used to produce sunflower oil in water emulsions. Span 80 and Tween 20 were used as surfactants in the dispersed phase and continuous phase, respectively. Both dead-end and cross-flow processes were investigated. Membrane pore diameter and cross-flow velocity dominated the final droplet size. The droplet size yielded was consistently in the nanometer range and exhibited low polydispersity (<0.2). In particular, the smallest average droplet size range of approximately 120 nm was obtained when a 25 nm membrane was used in a cross-flow configuration. Models developed for micrometer-sized emulsions produced an overestimation of the nanoemulsion droplets in this work of up to 180 times. A modified version of the model developed by Peng and Williams is proposed here with good agreement for nanometer-sized emulsion droplets.