Jonathan McPhillips, 28, died four days after being stabbed in Islington.
Police were called to Upper Street at around 12.40am on 25 February 2017.
Mr McPhillips, from London, was taken to hospital but died on 1 March.
A 17 year-old man was also stabbed during the incident.
Three men and a woman have so far been arrested during the investigation.
Detectives are appealing for witnesses to an altercation between two groups of youths.
Detective Chief Inspector Dave Whellams said: "Jonathan's family have been left completely devastated by the circumstances which led to his death. His two young daughters will now grow up with a devastating loss that has deprived them of the chance to know their father.
"Almost a week has passed since the incident and we continue to piece together the events which took place in the early hours of last Saturday morning.
"At this early stage this appears to be motiveless attack and we have established that Jonathan, who was in the company of seven or eight friends out enjoying the evening. The group was approached by six or seven males, an altercation occurred and Jonathan was fatally stabbed.
"The Upper Street area is usually very busy on a Friday night into the weekend, and we know that there were a number of people out and about who would have seen the altercation or the stabbing. I am urging anyone who witnessed the incident or has any information to come forward. It's important that we progress this investigation and trace the people involved and this can only be done with your help.
"I am also appealing to the friends and family of those who are believed to have carried out this attack. If you have the slightest indication that someone who you know may have been involved I would urge you to make the police aware of your concerns."
Any witnesses or anyone with any information is asked to call the incident room on 020 8345 3775, or to give information anonymously contact Crimestoppers on 0800 555 111 or visit crimestoppers-uk.org.