This research investigates the evaluation of the local friction drag of the turbulent boundary layers over cavities. Two indirect methods, including the composite profile method and the modified Clauser's chart method, were used to estimate the local friction drag of the turbulent boundary layers over a cavity array at four different downstream locations from the first row of the cavity array. Hot-wire probes were used to measure flow velocity at three different free-stream velocities. This resulted in a Reynolds number based on a momentum thickness from 1212 to 3040 and an inner-scaled cavity diameter from about 18 to 44. It was found that the friction coefficient of turbulent boundary layers over the cavity array was decreased compared with those over a smooth wall. A maximum reduction of about 15% was observed in the local skin friction of the turbulent boundary layers over the cavity array, compared to those of the turbulent boundary layers over a smooth wall. It is noted that the reductions in the local friction coefficients, measured at about 14 cavity array diameters from the array trailing edge, were smaller than those measured above the cavity array.