The attack happened on Thursday night at 10.05pm while a 39-year-old man and 39-year-old woman were at their house in Applegate Drive, East Kilbride.
Police say the men entered the house and threatened the couple with a knife.
The suspects then made off with a mobile phone and were last seen driving away in a small black van.
Although the couple were not injured, detectives say they were extremely shaken following the robbery.
The first suspect is described as 5ft 2in tall, aged between 25-35 years and of slim build with fair hair. He was wearing black tracksuit trousers, a dark hooded top and dark training shoes.
The second man was 5ft 10 in tall and wearing black tracksuit trousers, a dark tracksuit top and dark trainers.
Both men had dark-coloured scarves over their faces.
Detective Constable Ross Philip said: “At this time, enquiries are ongoing to trace the two men responsible for this robbery and establish a motive for this incident.
“I would urge anyone who saw these two men acting suspiciously in the local area around the time of the robbery, or may have information on the small black van they used to contact us.”