The crash occurred near the town of Wolfenschiessen, about 50 kilometers (30 miles) south of Zurich, Nidwalden cantonal (state) police said in a statement. Nobody in the train was hurt.
Swiss public broadcaster SRF reported that the minibus, with four men and four women on board, was driving alongside the train when it took a right turn at a rail crossing. The rail crossing had a warning light but no barrier.
Swiss transportation workers union SEV said the crash could have been prevented, noting that there had been a similar accident at the crossing just two weeks earlier.
"We are deeply shaken and dismayed by this tragic accident," SBB chief executive Andreas Meyer said in a statement. "We extend our condolences to everyone affected.