"Her community and the whole country has been united in grief, and united in rejecting the well of hatred that killed her in what increasingly appears to have been an act of extreme political violence," Corbyn told a specially-convened session of parliament, which had been in recess for EU referendum campaigning.
Lawmakers from all political parties paid tribute to the Labour MP Cox for her work helping Syrians, refugees and promoting human rights.
Her murder happened just hours after the nationalist party, UKIP, unveiled a poster with a long line of refugees fleeing conflicts with the words "Breaking Point". The campaign was immediately compared to Nazi-propoganda and heavily criticised.
"I can only imagine Jo's reaction had she seen the poster unveiled hours before her death. A poster on the streets of Britain that demonised hundreds of desperate refugees, including hungry terrified children fleeing from the terror of ISIS and from Russian bombs," said Labour MP Stephen Kinnock, who shared an office with Cox.
"She would have responded with outrage and with a robust rejection of the calculated narrative of cynicism, division and despair that it represents. Because Jo understood that rhetoric has consequences. When insecurity, fear and anger are used to light a fuse then an explosion is inevitable," he added.
Her voice breaking with emotion, Labour MP Alison McGovern said: "When Jo spoke, Mr Speaker, we all listened. Why? Because the principles she drew on in that speech and life is the simple idea that we have more in common than that which divides us."
After the House of Commons session, lawmakers applauded as they filed out of the chamber to attend a memorial service in Westminster.