Justin Welby condemned "hate-filled attacks" and said those involved were using division as an excuse of prejudice and Cardinal Nichols, president of the Catholic Bishops' Conference of England and Wales said that people need to unite, not divide.
Archbishop Justin warned some were using the EU referendum result as a "mere sham for their hatred to be expressed."
Reports of racism in the aftermath of the vote were "not acceptable", Cardinal Nichols said.
Archbishop Justin said in a statement: "We all need to reflect on what has been a tumultuous few days and ponder what is needed now.
"Firstly, I am very conscious of the Polish community in Hammersmith or of people confronted by banners in Newcastle.
"This upsurge of racism, of hatred towards others is something we must not tolerate.
"We have to say this is simply not acceptable in a humane society and it should never be provoked or promoted.
"Racism and hatred must never be tolerated, but there is no need for fear.
"We always place our lives at the foot of the cross; in the hands of Jesus."
He was speaking after police were placed on heightened alert for a spike in hate crime after a flurry of incidents sparked fears of a wave of racial abuse in the wake of the EU referendum.
Mayor of London Sadiq Khan asked the Metropolitan Police, Britain's largest force, to be "extra vigilant" for any rise in cases.
The National Police Chiefs' Council has also revealed that there was an increase of reports to an online hate crime reporting site between Thursday and Sunday compared to the corresponding period four weeks ago.
Cardinal Nichols stressed that "we have an important job in defining the horizon against which we live," and said people need to work hard to make their values come to life.
"I am sure that every leader needs to reflect on our failure to listen and to give voice to those who feel voiceless," he said.
"We need to grasp again our basic sense of purpose; in living together, creating together and fashioning a society.
"It is that sense of purpose that we may have lost focus of; believing that the purpose of politics is to manipulate power; the purpose of business is simply to make profit for a few. This challenge has been with us for a while now.
"Our purpose must be our common good, the good of all with no one excluded.
"Our politicians have to deal with their issues, businessmen and banks with their issues, but the fundamental purpose is to build a world in which strength is used for service and no one is excluded."
The leader of Catholics stressed how important it was for the whole of the nation "to speak for everyone," and not let the referendum divide us.
He said it was key to work together to tackle the "world's problem, which are great and challenging."