We report studies of the structure and dissociation dynamics of the Mg2H2O+ ion-molecule complex. The weakly bound clusters are formed in a supersonic molecular beam equipped with a laser vaporization source, mass-selected, and studied by laser photofragmentation spectroscopy in a tandem time-of-flight mass spectrometer. Broad structureless molecular absorption bands are observed in the red (610-745 nm), the green (515-595 nm), and the near UV (335-390 nm) spectral regions, and are assigned to transitions localized on the Mg-2(+) chromophore. Three daughter ions (Mg+, Mg-2(+), and MgH2O+) have been observed. We have Studied the competitive branching into accessible product channels as a function of photolysis wavelength in these bands. In order to understand the dissociation mechanisms we have carried out ab initio calculations of the ground and low lying excited states of the Mg2H2O+ complex. These studies give insight into the dissociation dynamics. Results from these experiments are compared and contrasted with previous work on the photodissociation of Mg2CO2+.