Não há uma descrição principal do primeiro contato formal da Federação com a União Cardassiana. Eles encontram indivíduos Cardassianos em Jornada nas Estrelas: Enterprise - um Borg Cardassiano, e o que parece ser um corpo Cardassiano na estação automatizada de reparos em "Parada Morta" - mas estes obviamente não respondem à pergunta. do primeiro contato oficial.
Existem algumas contas (conflitantes) em vários romances e quadrinhos da Trek. Por Memória Beta :
By some accounts, first contact between the Federation and the Cardassian Union occurred circa 2321, on the human colony world of Juhraya. (VOY - The Brave and the Bold, Book Two novella: The Third Artifact)
This conflicts with Day of the Vipers, which states that the Cardassians were already engaged in "pointless, unresolved conflicts" with the Federation by 2318. This implies a first contact date sometime before or during 2318.
The first official talks between the Cardassians and the Federation took place in 2327, however the Cardassians were using the talks as a pretense to disrupt relations between the Federation and Legarans to make Legara IV susceptible to annexation by the Cardassians. Fortunately the plan was uncovered and the Federation placed extra Starfleet protection around Legara. (TOS comic: "Enter the Wolves")