The politician spoke out after following pressure to clarify his stance and criticism for not being more open about his views.
Speaking with the BBC, he said: "I don't believe gay sex is a sin.
"I take the view that as a political leader though my job is not to pontificate on theological matters."
In an interview last week, Mr Farron did not say whether or not homosexuality was a sin.
Following criticism from celebrities and fellow politicians, he said one day later in the House of Commons he did not think being gay was a sin.
Mr Farron then faced calls to be unambiguous over his views specifically on gay sex.
Asked in the BBC interview why he had not made his views clear sooner, he said: "I was asked the question early on and I didn't want to get into a sort of series of questions unpicking the theology of the Bible.
"What I want is to make sure we deal with something that's become an issue."
Trying to draw attention back to the General Election in June, Mr Farron added: "we need to be talking about big issues - health, social care, education, whether we're in the single market or not."