Chemoselective hydrogenation of nitroarenes under industrially viable conditions is one of the attractive reaction for chemical, pharma, and pesticide industries. Herein, we report a reusable, stable, and renewable carbon-supported cobalt nanocatalyst (Co/MA-800) for the chemoselective reduction of structurally diverse nitroarenes with molecular hydrogen. The Co/MA-800 nanocatalyst was prepared via simple and straightforward carbonization of macroalgae and characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, H2-temperature programmed reduction, N2 adsorption-desorption, and Raman spectroscopy. The cobalt content in Co/MA-800 is determined by inductively coupled plasma-atomic emission spectroscopy analysis. Furthermore, we show the hydrogenation of four marketed nitro pharmaceuticals that were selectively transformed to the respective primary anilines in excellent yields. We also demonstrate the synthesis of two industrially relevant key pharma intermediates on the ∼1 g scale, which are further employed in the preparation of drug compounds such as Linezolid and Tizanidine. The Co/MA-800 nanocatalyst was also active for the reductive amination of bezaldehyde and nitroarenes to achieve imines in good yields. In addition, the Co/MA-800 nanocatalyst is recycled 5 times without significant drop in catalytic activity. © 2020 American Chemical Society. All rights reserved.