The facility will fund Leon’s expansion plans both nationally and internationally as well as allowing the group to restructure existing debt.
The news comes as the group opens its 30th site at the entrance to High Street Kensington underground station in London.
It is Leon’s eighth new site in 2015 with another three openings lined up before the end of the year - including a flagship Hammersmith Broadway restaurant opening at the beginning of December.
The company is looking at locations such as Manchester and Glasgow with a view to open in the cities next year.
Leon co-founder and chief executive John Vincent said: “More restaurants means we can reach more people and employ more people.
"The people who join Leon are very special. They are often young, highly spirited and highly talented. We know we have a great responsibility to help them thrive and grow. Each new restaurant makes it possible to give greater responsibility and greater chances to my fantastic colleagues.”
Leon will be running a celebratory Facebook competition today, giving away 30 meals to keen customers.
On the funding, Vincent said: “Throughout the process of getting to know each other, I have been struck by the desire of HSBC to understand our business and help us grow.
"They have toured our kitchens, walked into our big fridges, talked to our managers and eaten our food. I believe that they are backing us because they believe in the culture that everyone at Leon is creating.”
Amanda Murphy, HSBC UK head of corporate banking, said: “HSBC is proud to support ambitious British businesses and we look forward to helping Leon achieve its goals to grow, both at home and abroad.”