The 26-strong bar and restaurant operator saw sales peak at 24 per cent in the first week of December and in the week before Christmas Day while sales rose 11 per cent for the last week of December.
Chief executive Paul Harbottle said sales were ahead of the forecast and indicated that customers were determined to enjoy the festive break. Pre-selling of party tickets also helped boost sales he said.
"The mood in our venues was very good with people clearly out to let their hair down, he said. "We had a flat November but it's clear now that people were holding back for December."
New Years Eve
Despite sales rising overall for the five weeks of the festive period, spend-per-head for New Year's Eve dropped on the previous year, although there was an increase in the number of customers.
Harbottle added: "We are very pleased to have beaten our forecasts in December. We all have a bit of a smile on our faces. It means that we are going into January with a lot of wind in our sails."
Atmosphere opens its next site, a Chicago's in Stourbridge, in the West Midlands, in March this year. The group, which formed last year, is planning to double the size of its estate by the end of next year by opening more Chicago's and Modello Bar & Kitchen sites.