The fight took place outside a petrol station in Guildford in February, The Mirror reports.
Allegedly, Dappy - aka Costadinos Contostavlos - arrived in a car with another man, and the pair approached a group of two girls and three men outside the garage at 3.30am.
The pair reportedly asked the girls to join them, and when they refused, one of the two spat at the women. The altercation then broke out.
The three men who were with the two girls received serious facial injuries.
Dappy was arrested and has been bailed until May, while his companion was arrested and bailed until this month.
A Surrey police spokesperson said: "Police are investigating an incident which happened on the forecourt of the Shell garage in Woodbridge Road, Guildford, on Tuesday, February 28.
"Three men were assaulted and received serious facial injuries in the attack. A 27-year-old man and a 24-year-old man were both arrested on suspicion of affray."
Dappy recently reunited with N-Dubz bandmate Fazer in the studio.
He had previously spoken out about his cousin Tulisa Contostavlos's sex tape scandal, suggesting that Fazer was trying to use the incident to get Tulisa back.
Watch the video for N-Dubz's 'Morning Star' below: