It happened at around 08:00 on Friday 4 November.
The incident involved a white van as well as the pedal cyclist.
It started on the Weighbridge Roundabout, before continuing as both people made their way onto the Quay towards the pedestrian traffic lights near to the Weighbridge clock tower.
It was in this area that the cyclist was knocked off their bike.
Guernsey Police would like to speak with anyone who may have witnessed the incident, in particular anyone who was waiting to cross at the pedestrian traffic lights.
Anyone with information or dash cam footage should contact police HQ on 222 222 or Crimestoppers anonymously on 0800 555 111.