The 53 year old man, who walks with a frame, boarded a 253 Borders Bus service outside the Bridgend Hotel in East Linton at around 3.40pm on Wednesday 4th July.
Whilst getting on the bus and during the journey, the man was verbally and physically abused by a man and two women who also boarded outside the hotel.
The victim got off the bus at around 4.40pm at Hardgate in Haddington and the group continued to follow him with more abuse shouted.
PC Deborah Hoban of Haddington Police Station said: “This was a disgusting attack on a vulnerable man who managed to make his way to the police station where he received medical treatment. He was extremely shaken but fortunately not seriously hurt.
“I’m keen to speak to anyone who witnessed this incident in East Linton and Haddington or anyone who may recognise those involved.”
The man is described as wearing a green t-shirt with writing on it, and the women had blonde highlighted hair.
Anyone who may be able to assist this investigation should call 101 quoting reference 2815 of 4th July, or the independent charity Crimestoppers anonymously on 0800 555 111.