Uniform, porous poly(D, L-lactide-co-glycolide) (PLGA) beads with controllable pore sizes were prepared using an unstable water-in-oil (W-O) emulsion and a simple fluidic device. Optical micrographs revealed that the unstable emulsion phase-separated into two phases: the top layer rich in large water droplets and the bottom layer rich in small water droplets. When a syringe with a luer tip offset from the barrel was used, we could selectively introduce each layer of the phase-separated emulsion as a discontinuous phase into the fluidic device while a poly(vinyl alcohol) (PVA) solution was used as the continuous phase. The resultant water-in-oil-in-water (W-O-W) droplets evolved into PLGA beads with pores both in the interior and on the surface after the organic solvent had evaporated. Porous beads prepared using the top layer exhibited larger pores and windows interconnecting the pores than the beads obtained from the bottom layer. To show the effect of pore size on cell growth, we cultured fibroblasts in the beads with small and large pores. Fluorescence micrographs and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay confirmed a high density of viable cells in the beads with large pores. These results suggest that the beads with large pores could provide a more favorable environment for cells and thus be potentially useful for tissue engineering and cell delivery applications.