The man, only identified as a 40-year-old French national based in Italy, had tried to smuggle the tusk into Switzerland on a train from Frankfurt to Zurich on Sunday, border police said in a statement.
The tusk, measuring 90cm and weighing 4.5kg, has been confiscated and handed over to species protection authorities in Basel, police said, adding that the Frenchman would face criminal charges.
The seizure of raw ivory is rare in Switzerland, the ATS news agency reported, stressing it was more common for customs officers to come across smuggled ivory that has already been shaped into sculptures and other precious objects.
The international trade in elephant ivory, with rare exceptions, has been outlawed since 1989 after elephant populations in Africa dropped from millions in the mid-20th century to some 600 000 by the end of the 1980s.
Yet poachers continue to slaughter elephants to lay their hands on their precious ivory and the illegal trade in the white gold continues to boom.
On Tuesday, Kenyan wildlife rangers said poachers had slaughtered a family of 11 elephants in what they said was the worst single such killing in the country in 30 years.
And last week, officials in Hong Kong seized more than a ton of ivory worth about $1.4m in a shipment from Kenya.