The accident happened on the Avenue de Rhodanie in Lausanne's lakeside district of Ouchy at around 5pm, according to Swiss media.
The driver of the van, a Lausanne man in his 60s, had just overtaken a car that had slowed down in front of him when he hit the pair, who were walking across a pedestrian crossing.
According to 20 Minutes the couple, named as Adrien and Diana, were walking with his sister when the vehicle struck, but she managed to avoid being hit.
The scene was attended by 19 police officers and two ambulances. Psychological support was offered to those who witnessed the events.
An investigation has been opened to determine the cause of the accident.