We compute the elliptic flow v2 of thermal photons in a strongly coupled plasma with constant magnetic field via gauge/gravity duality. The D3/D7 embedding is applied to generate the contributions from massive quarks. By considering the cases in 2+1 flavor super Yang-Mills analogous to the photon production in quark gluon plasma, we obtain the thermal photon v2, which is qualitatively consistent with the direct photon v2 measured at the relativistic heavy ion collider at intermediate energy. However, due to the simplified setup, the thermal photon v2 in our model should be regarded as the upper bound for the v2 generated by solely a magnetic field in the strongly coupled scenario. © 2014 American Physical Society.