Cardinal Vincent Nichols said "indiscriminate violence is never justifiable" but added that "specific use of weapons in a defensive mode" would be ok.
Prime Minister David Cameron is currently trying to gain enough support from MPs to order the RAF to drop bombs on IS in Syria.
Currently British war planes are only involved in action in Iraq.
Labour leader Jeremy Corbyn has refused to support strikes in Syria but Cardinal Nichols has signalled he agrees with the PM's position.
He said: "While there is a duty on us to pray, and while there is a duty on us to stand together, there is also a duty that those who barbarically threaten other individuals need to be stopped.
"And I don't think there's any doubt that effective action is called for to stop the actions and the activities of ISIS.
"Now one of the features of those who have to take responsibility for doing that is that they have at their disposal now methods of defence that are very precise - modes of attacks and bombs.
"While I am at a distance from all of that I can say indiscriminate violence is never justifiable."
He went on: "Specific use of weapons in a defensive mode is defensible."
The Cardinal also revealed to Premier he supported the police having a 'shoot to kill' policy where terrorists are concerned.
He said: "If my life is threatened I'd be very glad indeed if a policeman is nearby and stopped the person who was threatening me in his tracks.
"I think that's a proper course of action to take."
He was speaking after Catholic leaders met at the Bishops Conference to discuss a number of matters with a particular focus on the refugee crisis.
Cardinal Nichols said that he thinks that there is a "readiness in this country to accept more than 20,000 over the next five years."
The Prime Minister, David Cameron has said that the UK will take in 20,000 Syrian refugees by 2020.
Cardinal Nichols said that the fear of the few cannot be cast onto the many and told Premier that every refugee needs to be treated with respect.
He expressed sadness that the Muslim community was forced to pay for newspaper adverts declaring their disgust with the terror attacks and reiterating that IS do not represent Islam.
Listen to Premier's Hannah Tooley speak to Cardinal Nichols here:
