Conductive hydrogels play a crucial role in advancing technologies like implantable bioelectronics and wearable electronic devices, owing to their favorable conductivity and appropriate mechanical properties. Here, we report a novel bottom‐up approach for crafting conductive nanocomposite hydrogels to achieve enhancing conductive and mechanical properties. In this approach, new poly(ɛ‐caprolactone)‐based block copolymers with sulfonic groups were first synthesized and self‐assembled into uniform polyanionic nanoplatelets. Subsequently, these negatively charged nanoplatelets, with sulfonic groups on the surface, were employed as nano‐additives for the polymerization of 3,4‐ethylenedioxythiophene (EDOT), resulting in poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/nanoplatelet complex with 3.8 times enhanced electrical conductivity compared with their counterparts prepared using block copolymers (BCPs). Blending the (PEDOT:PSS)/nanoplatelet complex with calcium alginate, nanocomposite hydrogels were successfully prepared. In comparison with hydrogels with (PEDOT:PSS)/BCP complexes prepared by a top‐down method, the nanocomposite hydrogels were found to show twice as strong mechanical strength and 1.6 times higher conductivity. This work provides valuable insights into the bottom‐up construction of conductive hydrogels for bioelectronics using well‐controlled polymeric nanoplatelets.This article is protected by copyright. All rights reserved