The An Education star was a guest at the A Small World event at the Gstaad Palace Hotel attended by media mogul Harvey Weinstein, Meryl Streep's daughter Mamie Gummer and actors Rightor Doyle and Waris Ahluwalia.
The event included a charity raffle of luxury prizes and Mulligan was asked to nominate a charity to receive funds from the event, so she chose the Alzheimer’s Society, a cause close to her heart as her grandmother is living with the condition.
Mulligan appeared to be overcome with emotion when she gave a speech, but the actress insisted she was merely out of breath after stepping outside to call her husband, Mumford & Sons frontman Marcus Mumford, and rushing back in.
She said, "I’m not emotional, I'm just out of breath. I've been running!... Well I am emotional too."
Mulligan previously in a statement, "I am committed to helping Alzheimer’s Society in any way I can. My family and I rely on the help of organisations like Alzheimer’s Society to help us understand the disease and guide us in the care of my grandmother."
The gala raised a total of $95,000 (£58,000) for the Alzheimer's Society, the U.K.'s leading care and research charity for sufferers of Alzheimer's disease and other forms of dementia.