They were quickly released and transported to Banjul airport where they were deported to neighbouring Senegal.
Two journalists working for the Arabic-language service of international news organisation Al-Jazeera were held by security forces in The Gambia and deported, Gambian and Mauritanian sources told AFP on Monday.
The channel's Mauritania bureau chief Zeinebou Mint Erebih and cameraman Mohamed Ould Beidar were taken away from their upmarket hotel by plainclothes officers and detained on Sunday night, sources close to the journalists said.
They were quickly released and transported to Banjul airport where they were deported to neighbouring Senegal, according to Mauritanian sources.
The pair are believed to have entered the country on Tuesday, five days after a contested presidential election was held.
Al-Jazeera journalists were refused accreditation prior to the December 1 vote won by opposition leader Adama Barrow after 22 years of rule by President Yahya Jammeh, who is now challenging the result.
The network is well known in The Gambia for broadcasting several hard-hitting reports including of street protests in April that led to the jailing of dozens of opposition figures.
Separate sources close to the Gambian communications ministry said the journalists had recently requested an interview with minister Sheriff Bojang, but were told Al-Jazeera was "banned" in the country.
Erebih and Beidar succeeded in interviewing president-elect Barrow, however, with the meeting also published in English and posted online.