The Ukip leader said that prior to Ms Cox’s murder, the Brexit campaign had “momentum” that may have been lost as a result of the killing.
He also described the murder as an act of “one man with serious mental health issues” that should not be allowed to influence the campaign.
Speaking to Peston on Sunday he said: “I think we had momentum before this terrible tragedy,” he said.
“When you are taking on the establishment you need to have momentum. I don’t know what’s going to happen over the next three or four days.
“It’s difficult to tell. But those who have made up their minds to leave – I think they will go out and vote.”
Mr Farage was also condemned by the Labour MP Yvette Cooper for suggesting that he had been a “victim” of hatred in politics.
Mr Farage denied that he was responsible for whipping up hate against immigrants and added: “I think I’ve been a politician that has been a victim of it [hatred] to be honest with you,” he said.
But Ms Cooper said: “Nigel Farage is still trying to whip up fear and hatred towards refugees who are fleeing from conflict. It was extremely ill-judged of him describe himself as a victim.”
Earlier, one of the Leave campaign leaders, Michael Gove, admitted he "shuddered” when he saw a controversial anti-migrant poster designed to convince voters to support Brexit.
The poster, depicting a line of desperate refugees trying to reach Europe, was launched by Mr Farage last week under the headline "Breaking Point".
It was widely condemned by the Remain campaign. But today even Mr Gove said the poster was entirely inappropriate as part of efforts to persuade voters to pull out of the EU..
“When I saw that poster I shuddered,” he told The Andrew Marr Show. "I thought it was the wrong thing to do.”
However, Mr Gove went on to defend statements made by the Vote Leave campaign on the number of Turks who could come to the UK if we stayed in the EU.
He said such claims were justified on the grounds that it was British policy to support Turkey’s membership of the EU.
On the same programme the Labour leader Jeremy Corbyn also attacked the Ukip poster describing it as “appalling”. He said it showed the extent to which the “far right” had captured the Brexit campaign.
On Monday, MPs from different political parties could give up their tradition places in the House of Commons tomorrow in a show of unity in memory of Ms Cox.
Parliament is due to be recalled on Monday to allow MPs to pay tribute to the Labour MP, who was murdered outside a constituency surgery last week.
Under a plan being considered, MPs would not sit along normal party lines for the debate but instead spread around the chamber.
Jeremy Corbyn said he had heard the idea suggested and was interested in it. “I received that suggestion last night,” he told the Andrew Marr Show. “We’re thinking about that."
He added: “An MP dies and it is an attack on all of us. In her memory we have to create a more tolerant society.”
The EU referendum debate has so far been characterised by bias, distortion and exaggeration. So until 23 June we we’re running a series of question and answer features that explain the most important issues in a detailed, dispassionate way to help inform your decision.