Koryo Tours announced via its website that it had been informed that "foreign runners" will not be allowed to take part in April's Pyongyang Marathon - the firm's Twitter account making it clear that the restriction was due to "the fear of the spread of Ebola."
The move was also confirmed by Young Pioneer Tours.
Last October, North Korea already imposed a ban on international tourists in response to a global panic surrounding Ebola - which has claimed nearly 9,500 lives in the last year, according to the World Health Organisation.
Any foreign nationals still looking to visit the reclusive state have faced a 21-day quarantine period.
While Koryo Tours - which described the ban as "very disappointing" - has not put a date on when it will be lifted, Young Pioneer is expecting Pyongyang to end the measure "very soon within the coming weeks."
The whole episode is not without precedent - North Korea shut out foreigners for several months in 2003 in an effort to escape the SARS virus.