Beryllium–carbon dioxide cation complexes Be(CO₂)_n⁺ are produced by a laser vaporization-supersonic expansion ion source in the gas phase. Mass-selected infrared photodissociation spectroscopy supplemented by theoretical calculations confirms that Be(CO₂)₄⁺ is a coordination saturated complex that can be assigned to a mixture of two isomers. The first structure involves a bent CO₂⁻ ligand that is bound in a monodentate η¹-O coordination mode. Another isomer has a metal oxalate-type C₂O₄⁻ moiety with a C–C hemibond.