Officers say there are concerns for his welfare.
He was carrying a rucksack and a handheld bag at the time he went missing.
Sam is described as 5ft 9ins tall, slim, with shoulder-length black wavy hair, and is likely to be dressed all in black.
Anyone with information is asked to contact police quoting reference 2600221313.
A spokesperson for South Wales Police said: “Sam Singh, 27 from Penarth is missing and there is concern for his welfare.
“He was last seen on Tuesday, July 7 in Penarth carrying a rucksack and a handheld bag.
“Sam is described as 5ft 9in tall, slim, with shoulder length black wavy hair.
He is likely to be dressed all in black.
“If you have seen Sam or have any information on his whereabouts, please contact us ref 2600221313”.
