Abstract Microwave‐assisted synthesis of new 5‐alkylamino‐pyrazole‐4‐carbaldehydes was performed efficiently, with yields up to 99 % and short reaction times. Nucleophilic substitution of primary alkylamines with activated 5‐chloro‐1‐(2‐pyridyl)pyrazole‐4‐carbaldehyde was mediated by the “cesium effect”. The amination of deactivated 1‐aryl‐5‐chloropyrazole‐4‐carbaldehydes was also assisted by the cesium ion and catalyzed by copper(I).