The current study proposes a composite having a Au cluster embedded Within polyindole flakes (Au@Pin) as a promising electrocatalyst in formic acid oxidation. The present work provides a detailed study of the Au@Pin composite and its catalytic properties compared to those of a Au commercial electrode for oxidation of formic acid and a possible mechanism. The role of a morphology controlled composite and interaction of Au in the cages of polymers flakes are discussed for effective catalytic action of the material. The electrocatalytic oxidation of formic acid is carried out over a Au@Pin composite modified glassy carbon (GC) electrode. Voltammetric and chronoamperometric measurements show that a Au@Pin composite has better CO tolerance capability than Pin modified, bare GC and Au commercial electrodes. Electrochemical impedance spectroscopy (EIS) reveals consistent results and charge transfer mainly through a diffusion controlled process. On the basis of this EIS data, an equivalent electrical circuit is proposed. The higher catalytic activity of a Au@Pin composite toward formic acid oxidation in a mixture of 1.0 M HCOOH + 0.5 M H2SO4 electrolyte is observed in comparison to Pin modified and Au commercial electrodes due to the synergic effect between the Au cluster and Pin.