The Singapore Civil Defence Force (SCDF) told CNA it received a call for assistance at 6.30pm from 620 Upper Bukit Timah, the address of the church.
An SCDF team sent one person, understood to be the priest, to National University Hospital.
When CNA arrived at the church at about 7.50pm, at least eight police vehicles and 20 officers were seen on the church premises.
Minister for Culture, Community and Youth Edwin Tong condemned the attack.
“Very shocked to learn that a priest was stabbed at St Joseph’s Church about an hour ago during mass at the church. I understand that the subject has been disarmed and apprehended. The paramedics are attending to the priest. He is being conveyed to the hospital, and he is conscious. Praying that he is ok,” said Mr Tong in a Facebook post at 8pm.
“Such violence, of any form and for any reason, has absolutely no place in Singapore, let alone at a place of worship. The relevant authorities will investigate this incident and address it appropriately.”