Membranes can be defined as physical barriers allowing the selective transport of species. This tutorial aims to provide the basics of membrane technologies and materials, the fundamentals of the atomic layer deposition (ALD) technique, and, most importantly, to describe how to efficiently perform ALD on different membrane substrates. Membrane devices enable a considerable reduction of costs and environmental impacts for many industries, and there is a constant need to improve their operational performance. Atomic layer deposition (ALD) is a deposition technique enabling the preparation of high quality thin films on extremely high-aspect-ratio substrates with an excellent conformality and a thickness control at the nanolevel, a unique capability. Therefore, this technology can be applied for both pore size tailoring and interface engineering in membrane structures. Certain important aspects that must be taken into consideration when carrying out ALD on these highly porous ceramic or polymeric membrane substrates will be addressed, in order to achieve a conformal coating of pore walls. Finally, this tutorial will also provide specific case studies to illustrate how ALD can be applied to various membrane devices and improve their operational performance. Thus, by providing this knowledge of ALD for membrane applications, this tutorial will permit us to better exploit this emerging and growing field