The politician was approached as he walked through Westminster station at rush hour.
A video shows Mr Hancock being called a ‘murderer’ as shocked commuters watch on.
The MP, who came third in last year’s series of I’m A Celebrity… Get Me Out Of Here!, is understood to have been unhurt in the incident.
British Transport Police said in a statement: ‘We received a report of a man being assaulted and harassed at Westminster Underground station at 8.47am yesterday morning.
‘A 61-year-old man has been arrested on suspicion of common assault and a public order offence and remains in custody.’
Mr Hancock was accompanied during the video by a London Underground worker, who calls for calm during the footage.
The politician then sits down as a man informs the carriage of his presence and describes the politician as a ‘murderer’.
Mr Hancock, 44, was health secretary when the coronavirus pandemic struck and was a key figure in the lockdown restrictions and vaccine rollout that followed.
He resigned after leaked CCTV image showed him kissing an adviser in his office, in breach of his own social distancing guidance.
Mr Hancock angered colleagues and constituents by jetting to the Australian jungle to appear on the reality show but won some sympathy from TV voters to come third.
Having been stripped of the Conservative whip over the appearance, he said he would not contest his seat at the next election when he will step down.
A spokesperson for Mr Hancock said the incident was an ‘unpleasant encounter’.
They added: ‘Matt wants to put on record his thanks to Transport for London and the British Transport Police for their extraordinary work.’
Enquiries into the incident are ongoing.