This paper experimentally investigates the performances of two bottom-hinged-flap wave energy converters (BHF-WECs) operating in tandem. Firstly, the inertia effects of a single BHF-WEC operating in isolation are theoretically and experimentally examined to show their negligibility in coastal-water applications with the non-dimensional wave number ∼ O(1). Experiments of two in-tandem BHF-WECs with separation distance (d) varing from 0.5λ to λ (incident wavelength) with increment of λ/16 are then conducted in a small wave basin. Hydraulic pumps are used as the power take-off and their forcing characteristics as an energy damper are determined using a rating platform. Time-series images of flapping motions of the BHF-WECs, recorded with high-speed cameras, are analyzed using a processing and analysis procedure based on the correlation algorithm to evaluate their capture factors (CF). The CF variations of the first BHF-WEC with d exhibit a sinusoidal wave form with wavelength of λ/2. The combined CF of the two in-tandem BHF-WECs is always greater than 1.0, indicating that the wave energy outside the frontal area is drawn via diffraction. It reaches the maximum at around d = 14λ/16 with λ/4 apart from the minimum at around d = 9λ/16 owing to the underlying mechanism of the Bragg Reflection.