AbstractIonic thermoelectric (i‐TE) gels can have a high thermopower, if the thermodiffusion of mobile cation/anion is decoupled, attracting increasing attentions. Herein, it is shown a high p‐type i‐TE thermopower of 41.8 mV K⁻¹ in agarose‐based ionic thermoelectric gels of AG‐x Na:DBS (AG: agarose, Na:DBS: sodium dodecyl benzene sulfonate). The exclusively high thermopower is relative to the successfully decoupling the thermodiffusion of cation Na⁺ and anion DBS⁻. A unique porous structure is formed due to the micellization of the amphiphilic DBS⁻ with the hydrophilic benzenesulfonic group attached to the hydrous agarose gel chains, while the hydrophobic alkyl chain point to the pore centers. As a result, the DBS⁻ micelles are almost immobile as compared with Na⁺, which can be reconsidered as a part of the gel matrix. The work shines a light on decoupling of cation/anion thermodiffusion through tailoring the microstructure of the quasi‐solid i‐TE materials.