St Malachy's Down and Connor Diocesan Seminary in Belfast has been operating for 185 years but is due to close down in September.
The Diocese of Down and Connor has blamed the closure on the discontinuation of philosophy classes offered at Queen's University of Belfast (QUB) which is where St Malachy's seminary students would study a range of degrees.
The seminary said in a statement: "The closure of the Department of Scholastic Philosophy at Queen's University and, more recently, the progressive discontinuation of modules in scholastic philosophy on offer within QUB have placed a great strain on the required philosophical training of clerical students in Belfast as a prerequisite for theological studies."
The seminary's remaining students will have to relocate their studies for priesthood outside of Northern Ireland, as St Malachy's was the only one.
The seminary said it's a sad moment, but the decision was in "best interests of the seminarians who are currently in formation".
"This decision has been taken with a certain sadness yet with trust in the providence of God, and with much satisfaction over what has been achieved through the diocesan seminary over the years," the statement added.
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