The paper investigates numerically the flow-induced vibration of both elastically mounted D-section and circular cylinder in tandem arrangement in the proximity and wake interference region at Reynolds number Re = 100. The problems are solved using in-house code based on level-set function-based immersed interface method (LS-IIM). Both elastically mounted cylinders have same diameter and mass ratio \(m^*\) = 2.0 with damping ratio \(\zeta \) = 0.005. The two cylinders are placed in tandem arrangement with varying gap ratios of \(G^*\) = 3.5–0.1. The circular cylinder is moved from wake interference region to proximity-wake interference region by decreasing the gap ratio. Our simulations reveal: (1) large amplitudes of vibration and wider lock-in for circular cylinder in tandem arrangement when compared to isolated; (2) over the range of \(G^*\) considered, the D-section cylinder shows both VIV and galloping response; (3) suppression of the galloping ability of D-section cylinder when the downstream cylinder at maximum proximity ( \(G^*\) = 0.1); and (4) three-stage transition of the vibration characteristics from VIV ( \(G^*\) = 0.1) to galloping (0.3 \(\le \) \(G^*\) \(\le \) 1.0) to wake-induced galloping ( \(G^*\) \(\ge \) 2.0) of the downstream circular cylinder when the gap ratio increases. The three-vibration response has distinct flow dynamics occurring in gap, and each flow state is discussed in this paper.