Before a minutes silence was held, a musician in the small crowd performed a version of the Bob Dylan song 'She was a friend of mine.'
The 41-year-old mother of two young children was shot and stabbed on Thursday while working in her Yorkshire constituency.
A 52-year-old man, Thomas Mair from Birstall, has been charged with her murder. Appearing before magistrates on Saturday he gave his name as "Death to traitors, freedom for Britain".
Emma Hutchinson, 32, is the women's officer for the Labour Party in Northern Ireland. Speaking outside Belfast City Hall today she said: "We came here to pay respects Jo Cox's life after she was so cruelly murdered. We just said a few words about her work, about her life and the sad loss to her family and especially to her husband Brendan and her two young children."
"I think it's possibly the first time an MP has been killed outside of terrorism for their political beliefs. She wasn't a big hitter MP, but she worked diligently for her constituents and further afield for the Syrian children.
She continued: "Across the water the referendum has stirred up some quite unsavoury opinions and a nasty debate at times, but it's great to see people speaking from a progressive voice today who won't be silenced and have come out in support of her to show she won't be forgot."
MP for South Belfast, the SDLP's Alasdair McDonnell, had known Jo Cox briefly during her first year in Westminster.
"Thursday was stunning for all of us," he said. "While MPs do suffer a certain amount of abuse and antagonism from people who get frustrated when an MP can't deliver perfection for them, you do not expect a colleague to be shot dead."
"To have somebody shot dead is quite frightening and intimidating for all of us."
"Jo was a tremendously passionate individual in the issues she took up, in particular Syria and the refugees."
"We have a particular solidarity here in Northern Ireland as MP's lost their lives. In South Belfast my predecessor Robert Bradford was shot and again Edgar Graham from the UUP was shot."
"We've had a sense of this and the pressure MP's are under, but no matter how and when it happens it's not acceptable and can never be justified."