Ali Babitu Kololo, 27, was found guilty of robbery with violence and kidnapping with intent to cause murder over the brutal raid by Somali pirates in September 2011.
He was handed the death sentence but is likely to spend the rest of his life in prison after Kenya halted its programme of public executions.
Sentenced to death: Ali Babitu Kololo (right)
was convicted of robbery with violence and kidnapping with intent to
cause murder at a court in Lamu, in Kenya
Kololo, a Muslim father-of-two, shook silently in the dock as magistrate Johnstone Munguti sentenced him during the two hour judgement hearing at a court in the coastal town of Lamu.
Mr Munguti said: 'I must tell you that I am obliged by the laws of Kenya to sentence you to suffer death for the first count, that is for robbery with violence.
'For the second count I sentence you to seven years in prison.'
Kololo was led from the court in handcuffs after becoming the first person to be convicted over the kidnapping of Mrs Tebbutt and the death of her husband.
The couple, from Bishop's Stortford in Hertfordshire, were enjoying a holiday when a gang of six men burst into their secluded beach cottage in the early hours of September 11 2011.
Mrs Tebbutt, 58, a social worker, was dragged from their bed and bundled into a speedboat which took her to Somalia.
She spent more than six months as a hostage in the war-torn country before being freed in March 2012.
Her husband, publishing executive David, 58, died at the scene after he was shot in the chest as he tried to protect his wife during the raid at the remote Kiwayu Safari Village.
Kololo, who previously worked at the luxury resort, was arrested the day after the attack and remains the only person to be charged in connection with the tragedy.
He admitted in court that he had helped lead the Tebbutts' attackers to their cottage but claimed he did so under duress after he was himself abducted by the gang.
Today the court dismissed that claim and said it was clear he had been the sixth member of the group.
Mr Munguti referred to evidence given to the trial by Mrs Tebbutt, who told how her captors had told her the sixth gang member had been arrested.
The magistrate said: 'Mrs Tebbutt was unable to positively identify you, although she could not rule you out.
'However, one of her attackers said somebody was left behind and that the guy was in big trouble in Kenya.
'On the evidence, that person could only have been you, because no other person was arrested and charged.'
Kololo, a devout Muslim, wore a pink T-shirt today as continued to deny his guilt.
Addressing the court in his own mitigation, he said: 'I have left everything to God. I abide by your decision.'
He added: 'I did not participate in the attack. The prosecution framed me.'
Two Metropolitan Police detectives were in court today to witness proceedings.
The pair were part of a team which flew out to help Kenyan police in the days after the attack.
Local detectives have said they continue to investigate the abduction but have acknowledged it could be difficult to track suspects who are believed to remain in Somalia.
Mrs Tebbutt this month published an account of her abduction and months as a hostage in a book about the tragedy.
Hidden terror: The Kiwayu Safari Village Beach where Mr and Mrs Tebbutt were attacked. Mr Tebbutt died in the struggle