Snow's comment, referring to pro-Brexit protesters who gathered in Westminster on the day the UK was meant to leave the EU, sparked more than 2,600 complaints that it was racist and offensive.
He had told viewers: "It has been the most extraordinary day. A day which has seen - I've never seen so many white people in one place.
"It's an extraordinary story. There are people everywhere, there are crowds everywhere."
Channel Four described the comment as "a spontaneous, unscripted observation" and previously said it "regretted any offence caused".
It said that the comment was "factually accurate" and that "Jon Snow, who is also a white person, told the public what he saw.
"Some have inferred that Mr Snow was making a negative comment about Brexit supporters and that there were racial overtones. That was not the case. There was no negative or pejorative language, tone, intent or implication behind it ... He was entitled to point to this unusual situation," it said.
While finding that the comment was not in breach, Ofcom reminded broadcasters to take "particular care" with "ambiguous statements" amid a "volatile public discourse surrounding Brexit".
It also issued the reminder about "ambiguous remarks" after ruling that a comment made by Nigel Farage on his LBC show, in the aftermath of Snow's comment, was not in breach.
Farage said Snow "should be attacked ... because of his terrible condescending bias".
He later clarified in the programme that he meant a verbal attack, not a physical one, saying: "Verbally, verbally attacked for his disgraceful coverage of the Leave rally."
Ofcom received seven complaints about the remark on LBC 97.3FM.
An Ofcom spokeswoman said in reference to both broadcasts: "We recognise that comments made by the presenters in these programmes had the potential to cause offence to viewers and listeners.
"However, we concluded that both unscripted remarks came during live programmes which featured a broad range of views about Brexit. The comments were also ultimately clarified.
"But we've reminded both broadcasters that ambiguous remarks, in programmes dealing with polarising political issues, should be put fully into context."