The photoionization and dissociative photoionizations of ethylenediamine have been studied both experimentally and theoretically. In experiments, photoionization efficiency spectra for ions NH2CHCH3+, NH2CH=CH2+, CH2NH2+, NH3+, NH2CH2CHNH2+ and NH2CH2CH2NH2+ have been obtained. In addition, the energetics of the dissociative photoionization is investigated with ab initio Gaussian-3 (G3) calculations. The computational results are useful in analyzing the dissociation channels near the ionization thresholds. With the help of the G3 results, the dissociation channels for the formation of the aforementioned fragment ions have been established.