N-methylamines are an important class of amines that find increasing applications in chemical, pharmaceutical, agrochemical and material industries. For their preparation, reductive N-methylation reactions employing CO2, formic acid, and (para)formaldehyde as renewable C1 sources have shown outstanding advantages compared to traditional methylation reagents, on standpoint of sustainable chemical processes. In this respect, significant efforts have been made on the synthesis of N-methylamines by catalytic reductive aminations. In this review, we discuss the recent advancements toward the base metal-catalyzed reductive amination of amines and nitroarenes including nitriles using CO2, formic acid, and (para)formaldehyde for the synthesis of diverse N-methylated products. © 2021 Elsevier Ltd