The terminal diarsene HAs=AsH ligand attracts special interest concerning its bonding relation in comparison to its isolable relative, ethene. Herein, by the methanolysis of [{Fe(CO)4}As(SiMe3)3] (1) the synthesis of [{Fe(CO)4}(η2‐As2H2)] (2) is reported, containing a parent diarsene as unprecedented side‐on coordinated ligand. Following this synthetic route, also the D‐labeled complex [{Fe(CO)4}(η2‐As2D2)] (2D) could be isolated. The electronic structure and bonding situation of 2 was elucidated by DFT calculations revealing that 2 is best described as an olefin‐like complex. Moreover, the reactivity of 2 towards the Lewis acids [{M(CO)5}(thf)] (M=Cr, W) was investigated, leading to the complexes [Fe(CO)4AsHW(CO)5]2 (3) and [{Fe(CO)4}2AsH{Cr(CO)5}] (4), respectively.