We report on a full spectroscopic characterization of the Nd3+ ion doped Ca3Ga2Ge3O12 garnet laser host for different ion concentrations ranging from 2.5×10−2 up to 2 at. %. The Judd–Ofelt formalism has been applied, from which the stimulated emission cross section corresponding to the F3/24→I11/24 laser channel has been determined. Excited state absorption cross section in the 1020–1090 nm region has been measured by using two beam spectroscopy, demonstrating that the 1060 and 1065 nm laser emissions are not affected by excited state absorptions. Finally, once the basic parameters are known, we have applied the mode overlap formalism in order to determine the Nd3+ concentration and crystal length which optimize the laser performance of an end diode pumped laser system. We have concluded that the maximum output power is reached when the Nd3+ concentration and crystal length are around 0.75 at. % and 0.6 mm, respectively