The diocese has invited offers of interest in the 7724sq m property, with a rateable value of $1,925,000, in South Dunedin.
The school closed officially in April, at the end of term one, with its pupils amalgamated into St Bernadette's and St Brigid's Catholic schools.
Diocese of Dunedin Catholic education director Tony Hanning said the school was built about 1948 as the former St Edmund's Catholic school for boys, but during the reorganisation of Catholic schooling in the late 1980s, St Patrick's School, which had been on various sites during its 130 years, was relocated to the site.
However, it had become extremely difficult for the St Patrick's board to operate and maintain the school in a financially viable way, he said.
The diocese had to recognise the changes to the demography of South Dunedin.
Diocese general manager Stuart Young said there was "reluctance" to the amalgamation, but reasonable attendance levels had to be maintained.
"We have to rationalise our stock," he said.
The Melbourne St property was now "surplus to our requirements" but had much promise.
"Potentially, I would have thought it would have made a great site for a medical centre or community centre for South Dunedin - that sort of facility would really fit with the ethos of the church.
"I think there is a lot of opportunity in South Dunedin for a pocket of land which could meet the needs of the community," Mr Young said.
However, he was realistic about the amount of serious interest it would receive given today's property market and people's growing aversion to low-lying flat land following the Canterbury earthquakes.
The money from the sale had not been earmarked for any specific item, but Mr Young believed reducing debt created when the diocese bought the Otago Polytechnic grounds in Tennyson St was a realistic possibility.
