Drug substances and drug products are pharmaceutical materials that require complete characterization during their development process and in preparation of their submission to regulatory filing for approval for human consumption. Nuclear magnetic resonance (NMR) is one of the most informative analytical techniques that characterizes organic materials, which are used as building blocks towards the synthesis of drug substances and common components of drug products during the development stages in the pharmaceutical industry. In this chapter, we describe the applications of NMR during the development process of drug substances and drug products from small molecule drugs. In the area of drug substance development, the topics selected are structure elucidation of drug substances and materials related to their production, in-process impurities, and impurities from stability studies, quantitation of drug substances and related compounds, relative configuration of drug substances, reaction monitoring during process development, and solid-state NMR (SSNMR) characterization of drug substances. In the case of drug product development, the topics selected are the structure elucidation of impurities during stability studies of formulated drug substances, SSNMR of drug products, and quantitation of drug substances in the formulated drug products. Examples from the literature are used to describe those applications.