In 2007, a gene homolog of CDO encoded by the gene Gm237 in the DUF164 family was identified as cysteamine dioxygenase (ADO). ADO is one of the only known thiol dioxygenases found in mammals. Both ADO and its partner cysteine dioxygenase (CDO) are non-heme iron dependent enzymes that play a crucial role in the biosynthesis of taruine/hypotaurine by insertion of a dioxygen molecule. However, ADO has been overshadowed by CDO as heavy research focus on CDO over the past decade has led to the elucidation of its structure and possible mechanistic properties. In an effort to further understand ADO’s mechanism and regulating role in vivo, this work will be focused on the mammalian hADO and trying to gain further insight on hADO’s structural features via crystallography work. Investigation of the crystallization parameters for hADO has elucidated several potential conditions. Detailed work on these crystallization parameters will be presented.