5‐Hydrazineyl‐3‐methyl‐1H‐pyrazole (1) was used as a starting material for the synthesis of novel pyrazolo[3,4‐c][1,2]diazepine derivatives 3, 4, and 6a,b by its reaction with acetylacetone, ethyl acetoacetate, and isatylidene derivatives 5a,b, respectively. Also, pyrazolo[3,4‐c][1,2]diazepine derivative 11 was synthesized via multicomponent reaction of 1, benzaldehyde, and malononitrile. Moreover, compound 1 was used for synthesis novel pyrazolo[3,4‐c]pyrazole derivative 7 by its reaction with isatin. In addition, pyrazolo[3,4‐c]pyrazole derivatives 18a–c were synthesized by treatment of 2‐cyano‐N′‐(3‐methyl‐1H‐pyrazol‐5‐yl)acetohydrazide (13) with aromatic aldehydes 16a–c. The newly synthesized compounds were valeted by means of analytical and spectral data. All newly synthesized compounds were screened for their antioxidant activities. Compounds 3, 13, 18b, and 18c showed higher radical‐scavenging activities.