Gel polymer electrolyte (GPE) are better replacement of liquid electrolyte for dye‐sensitized solar cell (DSSC) but they have low efficiency due to insufficient segmental motion within the electrolyte. By incorporating transition metal oxide nanofiller, it can improve the performance of DSSC due to the existence of cross‐linking center that provides interaction with polymer side chain and redox mediator. Two different transition metal oxides (namely, manganese oxide, MnO2 and cobalt oxide, Co3O4) were synthesized using sonochemical method and incorporated as nanofiller. Poly (vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate) (P(VB‐co‐VA‐co‐VAc)) as a host terpolymer and sodium iodide (NaI) as a dopant salt were used to formulate the composite gel terpolymer electrolytes (CGPEs). The two different shapes of nanofiller have impacted the performance of CGPE proven by the structural analysis. It was found that both systems, the highest ionic conductivity achieved at 2.5 wt% of MnO2 and Co3O4 content with values of 6.40 and 5.2 mS cm−1, respectively. Surprisingly, the performance DSSC of Co3O4‐based CGPE was higher due to the strong Lewis's acidity of Co3O4, which absorb more iodide ions into the surface and facilitating the ions mobility. CGPE containing 2.5 wt% Co3O4 yield the highest efficiency, with value of 3.69%.