Pultruded glass fiber‐reinforced polymer (GFRP) bridge decks distribute punctual vehicular loads to the underlying superstructure and can also act as the upper chord of hybrid main girders. The deck’s structural performance in both cases is influenced by its transverse behavior. The static bending behavior in the transverse‐to‐pultrusion direction of two GFRP bridge deck systems with trapezoidal (DS) and triangular (AS) cell cross‐sectional geometry was experimentally studied. Different load transfer mechanisms were found in DS (frame‐dominated) and AS (truss‐governed) depending on the cell geometry. The DS deck exhibited a lower apparent bending stiffness and degree of composite action between the face sheets than the AS deck, which was attributed to the lower transverse in‐plane shear stiffness provided by the trapezoidal core than by the triangular core. The system in‐plane shear moduli were estimated from the experimental deflection results.