Several hundred people joined the protests which were largely focused on the council's so-called Agenda Item 7, a fixture on the council's schedule exclusively devoted to resolutions condemning Israel's treatment of the Palestinians.
Israel is the only country with a dedicated agenda item, which is one of the main factors that prompted the United States to leave the rights council last year.
“This is not just a form of bigotry. It is a sign of intellectual and moral decay,” US envoy Richard Grenell told the crowd.
“Like a drug-addiction, anti-Semitism is both a disease and a source of comfort” for states that habitually condemn Israel at the UN, said Grenell, who stirred controversy in Germany last year over his stated ambition to promote conservatives throughout Europe.
The protests were organised by the Geneva-based NGO UN Watch, which seeks to flag alleged anti-Israel bias within the UN, among other issues.
As the protest took place, council members attending the Item 7 session were debating the results of a probe which found that Israeli troops may have committed crimes against humanity in their response to the Gaza protests last year.
Israeli officials have rejected the probe's findings and accused investigators of bias.
Santiago Canton, who headed the commission of inquiry, told reporters he also does not “personally agree” with Agenda Item 7.
But even though the probe was initiated by the arguably flawed Human Rights Council, “that doesn't mean the work of the independent commission cannot be objective,” he said.
“If (critics) want to discredit our report they should discredit (it) on the facts and the law.”
Israeli officials have said the commission ignored the violent threat posed by Gaza protesters and downplayed the role of Hamas in orchestrating the unrest.