Background: This is the first review on Poly(diphenylamine) and its nanohybrids which covers about 181 references demonstrating the brief discussion on the theoretical studies, chemical, electrochemical and other-phase preparation techniques, polymerization and oxidation-reduction (redox) mechanisms, physicochemical and electrochemical properties along with electrochemical sensors and spectroscopic applications on the detection of chemicals and biomolecules analysis applications. Objective: The main aim of this detailed report is merely to afford a survey of the literature existing on this multifunctional conducting organic polymer (poly(diphenylamine)) that provokes a pathway to innovations and discoveries in the near future claim its applications in multidisciplinary fields, especially in the detection of chemicals and bio-molecules applications. Methods: We discussed the overall studies on poly(diphenylamine) and its various nanohybrids, including copolymers, homopolymers, carbon-based, and metal/metal-oxide hybrids. The different synthesis methods of poly(diphenylamine) such as chemical/electrochemical/mechano-chemical polymerization in terms of morphology and electrical conductivity were briefly discussed. Conclusion: This review manuscript deliberates the various synthesis approaches and applications based on the multifunctional conducting polymer poly(diphenylamine) and its nanohybrids. This review provides an outlook and challenges ahead that ignites spotlight to innovations and discoveries in the near future claim its applications in multidisciplinary fields, particularly in electrochemical sensors and spectroscopic applications towards the detection of chemicals and bio-molecules.