In recent years Direct Formic Acid Fuel Cells (DFAFCs) have attracted interest as alternative energy sources. Formic acid is abundant as it is a by-product of acetic acid and formamide industrial production or it can be obtained from the oxidation of biomass. In addition, due to the capacity to use high concentrations of fuel, DFAFCs are effective at room temperature. This is due to the low permeability of the fuel through the membrane when compared to other liquid fuel Polymer Electrolyte Membrane (PEM) fuel cell systems such as Direct Methanol Fuel Cells where fuel crossover is a problem. DFAFCs can generate power densities of ~85 mW/cm² outperforming Direct Methanol Fuel Cells (DMFCs) with power densities of ~50 mW/cm². However, no fundamental studies of the intrinsic conductivity and stability of the PEM have been carried out with formic acid. Understanding how the PEM behaves under such highly acidic conditions is vital for ensuring the long-term performance and durability of such fuel cells, should they be used on a wider scale. A comparative analysis of proton exchange membranes of the Nafion family was carried out and the intrinsic conductivity, dimensional stability as well as its operational temperature was observed for its use in formic acid fuel cells. From the results obtained a high performance was observed using a polytetrafluoroethylene reinforce membrane (Nafion XL). The membrane displayed a higher resistance to dimensional change when exposed to a wide range of formic acid concentrations, showing a maximum increase of 10% of its planar dimension while other membranes such as Nafion 117&115 had a significantly higher increase up to 45%. Results indicated that a reinforced membrane could be more suitable for DFAFCs, not only by possessing a higher dimensional stability but also due to it having a higher hydrophobicity due to the reinforcement and the lower content of sulfonic groups present in the copolymer. These changes would address the dehydration of the membrane, a factor substantially affecting the performance of the cell. This dehydration is known to be the result of an osmotic drag occurring from the anode to the cathode of the cell, added to the low content of water present in the reservoir result of the high concentration of the fuel feed. From the studies carried out, Nafion XL also presented a lower dehydration than the commonly used Nafion membranes allowing it to reach higher current densities and power densities. At the same time by comparing the individual Nyquist plots obtained by the electrical impedance spectroscopy for the different membranes, it was evident that the overall resistivity of the reinforced membrane was substantially lower and its proton conductivity higher making it a more adequate membrane for direct formic acid fuel cells.