People are not "taking the right action at the right time" if they see someone with symptoms of a stroke, health experts say.
The Stroke Association said that acting fast can make a big difference in the outcome for stroke patients.
Almost a quarter of people (24%) wrongly believe that you have to wait for two stroke symptoms to appear before calling the emergency services, according to research from 2015.
It comes as Public Health England have launched its Act FAST campaign, urging people to call 999 if they spot just one of the symptoms.
How to recognise the symptoms of a stroke
The FAST test can help you better recognise the common signs and symptoms:
Facial weakness - Can the person smile? Has their mouth or eye drooped?
Arm weakness - Is one arm weak or numb? Can the person raise both arms and keep them there? Does one arm drift downward?
Speech problems - Can the person speak clearly and understand what you say? Ask them to repeat a simple sentence, like "The sky is blue." Is the sentence repeated correctly?
Time - to call 999 for an ambulance if any one of these signs occurs.
Although the FAST test can identify most strokes, occasionally a stroke can cause different symptoms.
According to NHS Choices, other symptoms and signs may include:
Complete paralysis of one side of the body
Sudden loss or blurring of vision
Problems with balance and co-ordination
A sudden and very severe headache resulting in a blinding pain
Loss of consciousness
Stroke Association Chief Executive, Juliet Bouverie said: "A stroke is a brain attack and acting fast makes a huge difference.
"You are more likely to survive a stroke and make a better recovery if you call 999 on spotting any one of the symptoms."
Public Health England's director for health and wellbeing, Professor Kevin Fenton, said: "Stroke is one of the leading causes of death in the country, and the faster someone experiencing a stroke gets emergency treatment, the more chance that person has of surviving and avoiding serious disability.
"It is crucial to Act FAST when you see any single one of the symptoms of stroke, and do not delay making that all-important 999 call."