The ceasefire was agreed between gangs known as Brothas and Loyal to Familia, reports newspaper Politiken.
An ongoing conflict related to organised crime in the Danish capital has been connected to a recent escalation of shootings in the city, including two that resulted in fatalities.
The newspaper received information on the ceasefire from sources connected to gangs close to the Blågårds Plads area of Nørrebro.
The agreement is reported to have been reached on Saturday night, with families connected to gangs in the Blågårds Plads and Mjølnerparken areas subsequently gathering peacefully on Sunday, according to the report.
Key individuals related to the gangs, as well as fathers' groups in Nørrebro acted as negotiators in an effort to reach the deal, writes Politiken.
Two members from the Loyal to Familia gang attended Sunday's gathering, according to the report.
Copenhagen Police said that it had not been informed of any ceasefire between rival gangs.
“We do not have any knowledge of it, so cannot comment,” duty officer Henrik Stormer of Copenhagen Police told Politiken on Sunday night.