About 24,000 people were stopped from leaving Nigeria in the 15 months to March because of suspicion they could become involved in militant Islamism, prostitution or slavery, the country's immigration agency has said.
Many of them were suspected to be heading to join militant groups such as Islamic State (IS), the agency added.
Others tried to reach "greener pastures" to escape poverty, it said.
Nigeria is Africa's most populous state, and has high levels of poverty.
It has also been hit by a six-year insurgency waged by militant Islamist group Boko Haram, which pledged allegiance to IS in March.
The agency said Nigeria was a "catchment area for recruiters because of the high number of jobless people" in the West African state.
It had therefore intensified immigration checks to bar young Nigerians with "doubtful intentions" from leaving the country.
"The terrorist group has a syndicate that arranges travel documents, visas, ticket and money for their recruits," it added, in a statement.
Officials were also tackling illegal immigration, said Chukwuemaka Obuah, the agency's spokesman.
"We have always had problems of Nigerians going abroad for greener pasture. We look at the age of the intending traveller and the person he is travelling with, put them by the side and profile them thoroughly," he added.
The UN's Office on Drugs and Crime estimates West African trafficking victims, many of whom come from Nigeria, make up about 10% of those forced into sex work in Western Europe.
Last week, India detained two Nigerian students for allegedly trying to cross to Pakistan with the aim of finally reaching Iraq to join IS, media reports said.
Boko Haram's alliance with IS may be motivating young Nigerians to join the Middle Eastern group, reports the BBC's Bashir Sa'ad Abdullahi from Nigeria's capital Abuja.
They may have also been influenced by IS propaganda available on social media sites, he adds.