Jammeh seized power during a 1994 military coup and has been labelled an Islamist autocrat, with Human Rights groups accusing him of abuses and repression of opposition.
Mr Barrow, who was once a security guard in UK high street store, Argos, gained a lot of support from those opposing the President. "He is leading the most credible challenge to Mr Jammeh’s power since his 1994 military coup," BBC Africa reports. Several previously better-known opposition leaders are in jail after taking part in a rare protest in April.
The results of the election are not expected to be announced immediately. President Jammeh has also warned his rivals against contesting the outcome of the vote. "Our election system is fraud-proof, rig-proof, you cannot rig our elections," he said. "There is no reason that anybody should demonstrate. Demonstrations are the loopholes that are used to destabilize African governments.''
Barrow, on the other hand, told the BBC that Gambians had been suffering for 22 years and now was the time for change.
"Voters know that I am genuine and ready for change and that's why they should trust me," Mr Barrow said.