Oxford University found it cut cases by a quarter and deaths by more than a third in a review of 14,000 patients.
Aspirins are already widely used to help protect people against strokes and heart problems, although many healthy middle-aged people do not take them because of the risk of side-effects.
But researchers said their findings – published by the Lancet – “tipped the balance” in favour of taking them.
They followed up four study groups over a period of 20 years to identify the impact of regular small doses of of the drug – the tablets given for medical reasons are often a quarter of a strength of those used to treat headaches.
They found it reduced the risk of the incidence of bowel cancer by 24% and of dying from the disease by 35%.
And even though regular aspirin use can have side-effects, the researchers said it was still worthwhile as on such low doses these tended to be relatively minor, such as bruising or nose bleeds.
One in 20 people in the UK develops bowel cancer over their lifetime, making it the third most common cancer. About 16,000 people die each year as a result of it.
The findings build on previous research on the issue, and come after the government announced earlier this month it was looking to start a new screening programme for bowel cancer for 55-year-olds.
Lead researcher Professor Peter Rothwell said the screening would provide the perfect opportunity for doctors to discuss with their patients about whether to take aspirin.
“To date, for healthy middle-aged people it has been a fine balance as to whether to take aspirins, but this tips it in my view.
“There is a small benefit for vascular disease and now we know a big benefit for this cancer. In the future, I am sure it will be shown that aspirin helps prevent other cancers too.”
‘Talk to GP’
He added those with a high risk of bowel cancer, including the obese and those with a family history of the disease, should give aspirin treatment a particular consideration.
Mark Flannagan, chief executive of Beating Bowel Cancer, said they were “very positive” findings and giving aspirin alongside the new screening programme should be looked at.
But he added: “Anyone considering starting a course of medication should first consult their GP.”