Ca+-C2H2 is produced in a molecular beam and studied with mass-selected photodissociation spectroscopy. A spectrum with sharp vibrational and rotational structure is measured near the Ca+ (P-2 <-- S-2) transition. Ca+-C2H2 has a pi-complex structure with a Ca+-C2H2 bond distance of r(0)(n) = 2.80 +/- 0.20 Angstrom, a vibrational frequency (Ca+-C2H2 stretch) of Delta G(1/2)(n) = 169 cm(-1), and a dissociation energy of D-0(n) = 18.6 +/- 5.0 kcal/mol. This is the first spectroscopic determination of these properties for an isolated metal cation n complex.