Thin film devices, e.g., multilayer thin film devices, that encapsulate cells for transplantation into a subject are provided. Also provided are methods of using and methods of preparing the subject devices. The thin film devices include a first porous polymer layer and a second porous polymer layer that define a lumen therebetween and encapsulate a population of cells within the lumen. The thin film devices can promote vascularization into the lumen of the device via the pores in the first polymer layer and/or second polymer layer; limit foreign body response to the device; limit ingress of cells, immunoglobulins, and cytokines into the lumen via the first and the second polymer layers; and release from the first polymer layer and/or the second polymer layer molecules secreted by the population of cells.