Prince Philip is expected to remain at the London Clinic on Harley Street for up to two weeks.
His admission to hospital came shortly after he attended a Palace garden party this afternoon.
The Duke, who is 92 next Monday, had missed an engagement at the palace on Monday night because he was feeling 'under the weather'.
A Palace spokesman said: 'His Royal Highness The Duke of Edinburgh has been admitted to the London Clinic for an exploratory operation following abdominal investigations. He is expected to stay in hospital for up to two weeks.'
Lord-Lieutenant of Nottinghamshire Sir John Peace attended today's garden party where he said 91-year-old Philip had been 'telling jokes' - but he would not divulge what they were about.
Speaking of meeting the Queen at the event, he said: 'It was wonderful to see the Duke of Edinburgh with her.'
A Palace spokesman said that the planned admission came after this afternoon's garden party.