The 83-year-old man was taken to the Royal Infirmary.
Eastbound traffic was blocked at West Register Street for an hour at around 10.45am before the road was closed causing tailbacks from the The Mound.
The road was re-opened shortly afterwards.
Emergency services were at the scene for what was understood to be a ‘medical call’.
A Scottish Ambulance Service spokesperson said “We received a call at 10.43am about an incident on Princess Street in Edinburgh. We sent one ambulance who conveyed an 83 year old male to the Royal Infirmary of Edinburgh”.
Join our Facebook group Our Edinburgh to share images and news from and around the Capital