The gesture stemmed from a chance encounter with a woman who needed help closing her window.
The restaurant, Shish, is located on the outskirts of London. Early last month, an elderly woman who lived in the neighborhood came in to the restaurant and asked if anyone could help pull down a window she was having difficulty reaching.
The staff didn't hesitate. And when the woman returned the next day to thank them, she told them how she'd be alone for Christmas.
Her situation reminded owner Serdar Kigili of his mother in Turkey, whom he hadn't seen in five years. The management team then came up with the plan.
The team first advertised on the restaurant's front window with a hand-written note: "No one eats alone on a Christmas Day! We are here to sit with you. 3 course meal for the homeless from 12-6pm. Any homeless or elderly are welcomed."
The post has now been shared more than 1,000 times on the restaurant's Facebook page.
It inspired more than 25 residents to volunteer their time helping out that day. And a group of taxi drivers in the area have also said they will shuttle the elderly and homeless to and from the restaurant for free.
"It's not about religion, language or culture. It's about community," one of the managers, Irfan Can Genc, told CNN.
The approximately 66-seat space will be open all day, serving starters of soup and cacik, a yoghurt-based dip and mains of chicken, vegetarian casserole or chicken shish. Traditional rice pudding will be offered as dessert.
Genc says that he hopes the store will set an example for the community and that other restaurants might grab hold of the holiday spirit of giving.