Amyotrophic lateral sclerosis (ALS) is a fatal and progressive neurodegenerative disease affecting upper and lower motor neurons with no cure available. Clinical and animal studies reveal that the neuromuscular junction (NMJ), a synaptic connection between motor neurons and skeletal muscle fibers, is highly vulnerable in ALS and suggest that NMJ defects may occur at the early stages of the disease. However, mechanistic insight into how NMJ dysfunction relates to the onset and progression of ALS is incomplete, which hampers therapy development. This is, in part, caused by a lack of robust in vitro models. The ability to combine microfluidic and induced pluripotent stem cell (iPSC) technologies has opened up new avenues for studying molecular and cellular ALS phenotypes in vitro. Microfluidic devices offer several advantages over traditional culture approaches when modeling the NMJ, such as the spatial separation of different cell types and increased control over the cellular microenvironment. Moreover, they are compatible with 3D cell culture, which enhances NMJ functionality and maturity. Here, we review how microfluidic technology is currently being employed to develop more reliable in vitro NMJ models. To validate and phenotype such models, various morphological and functional read‐outs have been developed. We describe and discuss the relevance of these read‐outs and specifically illustrate how these read‐outs have enhanced our understanding of NMJ pathology in ALS. Finally, we share our view on potential future directions and challenges. The neuromuscular junction (NMJ) is highly vulnerable and affected at the early stages of the pathogenic process leading to ALS. Advances in microfluidic technology and stem cell biology have led to the development of ALS‐on‐a‐chip models. This has provided new avenues for studying ALS disease mechanisms and for drug development. One important advantage of these models is their high spatial control over individual cell types, enabling studies on the contribution of each cell type to NMJ dysfunction. Furthermore, in recent years a variety of morphological and functional assays has been developed to facilitate analysis of NMJ (patho)physiology in microfluidic platforms.