Women often make men's doctors' appointments for them, research suggests.
Women make the call to GP surgeries
More than 80% of men claim they book themselves in to see their GP - but 39% of women say the truth is their wife or partner does it for them.
The Prostate Research Campaign UK said women's better awareness of health meant they could play a crucial part in spotting the disease in their partners.
The Men's Health Forum agreed that men are still bad at seeking help.
A campaign, called Ignorance Isn't Bliss, has been launched to get women to look out for signs of prostate cancer.
The disease is now the most common form of cancer in men, with 10,000 men in the UK dying from it each year.
Symptoms include frequent visits to the toilet in the night, difficulty urinating or a burning sensation when passing urine.
The MORI survey of 1,361 adults aged 40 and over found 89% of men do not know the purpose of the PSA (prostate specific antigen) test, which can lead to early detection of the disease.
However, 70% of women could name at least one of the symptoms.
The survey showed 77% of men discuss a serious health issue with women, including partners, before seeing a doctor.
Professor Roger Kirby, chairman of Prostate Research Campaign UK, said: "Undoubtedly, there is an inbuilt instinct in women to seek out information on illnesses and treatments because of their family role in society.
"The Ignorance Isn't Bliss campaign aims to extend this female health awareness and knowledge to prostate disease in order to benefit men with symptoms of prostate cancer."
Susie Hobday, wife of prostate cancer sufferer and campaigner Kit Hobday, said she and her husband had known nothing about the disease.
When it was picked up, he had an advanced form of prostate cancer.
She said: "I wish I had known more about prostate cancer and then I would have been in a position to insist on him being investigated earlier."
Dr Ian Banks, president of the Men's Health Forum, said: "Eighty per cent of all GP consultations with men take place because their female partner told them to go."
He said observant GPs can often detect a prostate problem in men, not because they go to the surgery but because their partners do.
"Women appear in their late fifties asking for sleeping pills when previously they have never had a problem," Dr Banks said.
"The reason is that their male partner is getting up to have a pee two or three times in the night because of an enlarged prostate.
"If GPs give the women the sleeping tablets, they are treating the wrong person."