Charged species formed in a laminar counterflow diffusion flame of methane and oxygen enriched air are studied numerically and experimentally. Mole fractions and concentrations of major individual charged species are predicted using a one-dimensional counterflow diffusion flame model. A 65 step chemi-ionization mechanism in addition to a 208 methane-air combustion mechanism is used to model the chemical kinetics of the flame. The numerical calculations predict electrons and H3O+ to be the most dominant negative and positive charged particles respectively. OH- is found to be the most dominant species amongst the negative ions. As a result the total positive ion concentration is approximately equal to H3O+ concentration. An experimental method of measuring electron and total positive ion concentration is used. Electric current is measured as a function of the voltage and volt-ampere characteristics are obtained at different points between the two nozzles of the counterflow burner. The Langmuir probe theory is used to calculate the spatial ion and electron concentrations from the voltage-ampere curves. The effect of thermoionization of the neutral species is also analyzed. The experimental results obtained represent a similar behavior as compared to the numerical results.