The attack happened at around 11.45am on Friday when the victim answered the door of his home in Ayr to a stranger.
The man brandished a knife and forced his way inside the Park Circus property, demanding money.
He then made threats about the pensioner’s family and forced him outside and into his blue Jaguar.
The attacker told the man to drive to a nearby bank to withdraw cash.
He went to the NatWest branch on Miller Road and was able to raise the alarm.
The suspect is then thought to have left the car and made off towards Ayr Shore.
Police believe he may have been watching his victim at his home in the days before the attack.
The suspect is white, aged between 25 and 30, clean shaven and well spoken.
He was wearing a dark jacket with the hood up and dark tracksuit bottoms at the time of the attack.
Detective Sergeant Craig Semple said: “This was an extremely distressing experience for the elderly man and thankfully he was not injured, however it is absolutely vital that we trace the individual responsible for this despicable crime.
“From inquiries carried out so far, we understand the suspect was seen in a lane behind Park Circus shortly before the incident took place.
“I would appeal to anyone who noticed a man matching the above description or anything at all suspicious in the area to please get in touch.”
En-route to the bank, the Jaguar would have been seen on Race Course Road before stopping in Fairfield Road.
Mr Semple added: “I would also appeal for anyone who saw a Jaguar parked outside the Fairfield House Hotel, or a man running away towards Ayr Shore, to come forward.
“We believe the suspect may have also been observing the victim’s movements at his home in the days leading up to the incident and I would urge anyone who has noticed any suspicious activity in the area recently to contact police.
“Extra patrols will be in the area to provide reassurance and I would encourage anyone with information or concerns to approach them.”
Police can be contacted on 101 or alternatively information can be given anonymously via Crimestoppers on 0800 555 111.