Conductive composite film containing multiwalled carbon nanotubes (MWCNTs) coated with poly(iron tetra(o-aminophenyl) porphyrin) (PFeTAPP) has been synthesized on glassy carbon, gold, and indium tin oxide (ITO) electrodes by potentiostatic methods. The presence of MWCNTs at the electrodes enhances the surface coverage concentration (Γ) of PFeTAPP. The MWCNT-PFeTAPP composite film produced on gold electrode has been used for electrochemical quartz crystal microbalance studies, which reveal enhancements in the functional properties of composite film due to the presence of both the MWCNTs and PFeTAPP. The surface morphology of the composite film deposited on an ITO electrode has been studied using scanning electron microscopy and atomic force microscopy. These studies reveal that there is an incorporation of PFeTAPP with MWCNTs. The MWCNT-PFeTAPP composite film exhibits promising electrocatalytic activity toward the reduction of O2 and H2O2 , which has been studied using cyclic voltammetry. Further, O2 reduction has been enhanced at the composite film with the help of myoglobin as a mediator. The MWCNT-PFeTAPP film’s sensitivity values are higher than the values obtained for PFeTAPP and MWCNT films separately. Finally, I-t curve study has been conducted for the amperometric detection of H2O2 at the MWCNT-PFeTAPP composite film. The amperometric results show higher sensitivity values than the results obtained with the voltammetric technique.