Cops said a "number of youths both male and female" caused chaos at a branch of the fast food chain in Plymouth, Devon.
Officers were called to disperse the crowd at around 12am on Friday after the youngsters started "being abusive towards staff and other customers".
A food ordering machine was also damaged, police said.
The children were either taken home or made to move on from the area once officers arrived.
Posting on Facebook, Charles Cross Policing Team said: "Do you know where your child is??
"Last night there was a large disorder at McDonalds Pomphlett Road Plymstock Plymouth.
"There were over 100 youths who were being abusive towards staff and other customers and a food ordering machine was damaged.
"Police were called and due to the number of youths both male and female 5 doubled crewed police cars and a police sergeant were deployed.
"Police evoked a dispersal notice and the youths were either taken home or dispersed from the area. All this happen at MIDNIGHT!!
"Parents please ensure that you know where your child is for their safe and the safety of the staff and general public.
"Action will be take by Police by way of the Anti Social Behaviour process and McDonalds will issue banning notices to cover the whole of Plymouth if this continues!"
People sought to clarify the situation online, with some claiming that a youth fundraiser had been organised nearby that evening - meaning a large number of children were in the area.
But others argued that the behaviour wasn't good enough in any context.
One said: "Get a curfew in..17 and under home by 9..And if its broken an night in jail and parents fined..We are too soft in this country...Far too soft.
Another added: "They have CCTV don't they? I would be posting pictures of the little darlings, so the parents can see what they are really like!"
A third posted: "What absolutely appalling behaviour."
Charles Cross Policing Team is part of Devon and Cornwall Police.