The liberal mayor met with Trump Wednesday, despite de Blasio's frequent criticism of Trump.
"It was important for me to explain to him how fearful people are in this city, in this country, that not just the rhetoric but some of the policies that have been proposed literally have people wondering whether their family members might be deported, whether because of their religion they are going to be discriminated against," de Blasio told CNN's Alisyn Camerota on "New Day."
De Blasio said Trump was gracious in accepting his criticism during their hour-plus meeting in Trump Tower, adding that Trump's immigration policy was a topic of conversation.
"(It was) candid, obviously, because there are real differences," he said. "What we are concerned about: There are some very petty crimes, nonviolent crimes, where I think this becomes a more complicated issue."
De Blasio said there had been an uptick in racially tinged violence in New York but it was too soon to attribute it to the rhetoric of the 2016 presidential campaign season. He also condemned reported attacks against Trump supporters.
The mayor also said he told Trump Steve Bannon, recently appointed as Trump's chief strategist, "did not belong" in the White House.
"Look, a lot of things happen in transitions," De Blasio said of Breitbart News' executive chairman. "I think when people look at someone associated with a website that has been divisive and extremist and, obviously, has talked about white nationalism, for example. There's a chance for the President-elect to rethink that person's role."