The proton-bound nitrogen dimer, N2-H+-N2, and its isotopologues were investigated by means of vibrational spectroscopy. These species were produced upon electron bombardment of mixtures of N2 (or 15N2) and para-hydrogen (p-H2) or normal-D2 (n-D2) during deposition at 3.2 K. Reduced-dimension anharmonic vibrational Schrödinger equations were constructed to account for the strong anharmonic effects in these protonated species. The fundamental lines of proton motions in N2-H+-N2 were observed at 715.0 (NH+N antisymmetric stretch, ν4), 1129.6 (NH+N bend, ν6), and 2352.7 (antisymmetric NN/NN stretch, ν3) cm-1, in agreement with values of 763, 1144, and 2423 cm-1 predicted with anharmonic calculations using the discrete-variable representation (DVR) method at the CCSD/aug-cc-pVDZ level. The lines at 1030.2 and 1395.5 cm-1 were assigned to combination bands involving nν2 + ν4 (n = 1 and 2) according to theoretical calculations; ν2 is the N2⋯N2 stretching mode. For 15N2-H+-15N2 in solid p-H2, the corresponding major lines were observed at 710.0 (ν4), 1016.7 (ν2 + ν4), 1124.3 (ν6), 1384.8 (2ν2 + ν4), and 2274.9 (ν3) cm-1. For N2-D+-N2 in solid n-D2, the corresponding major lines were observed at 494.0 (ν4), 840.7 (ν2 + ν4), 825.5 (ν6), and 2356.2 (ν3) cm-1. In addition, two lines at 762.0 (weak) and 808.3 cm-1 were tentatively assigned to be some modes of N2-H+-N2 perturbed or activated by a third N2 near the proton.