Eleanor Burke said the nearest working toilets were four carriages away - too far for her to reach or to find her way back from,
Ms Burke, 68, who suffers from aniridia, which affects the iris, said the problem had ruined her trip from London to Edinburgh to attend a board meeting for a visually impaired people’s project.
A spokeswoman for Caledonian Sleeper was unable to say what caused the glitch, but its new £150 million fleet has suffered from a series of technical problems which have included software locking toilets out of use.
Operator Serco has admitted some such problems have been due to human error, in some cases because of “people pressing the wrong buttons”.
However, it had been thought such teething troubles following the trains entering service last April had been solved.
Ms Burke, who uses a guide dog, was travelling with a 71-year-old friend who helped her reach a toilet at the other end of her carriage when they boarded after they found the accessible toilet beside her room was not working.
Her friend, whose room was in the same carriage, later found that the working toilet had also gone out of action, and found the nearest operating one four carriages away.
Ms Burke said: “I was very disappointed. I thought it would be nice to go on the sleeper and I had looked forward to it.
“I was hoping for a really enjoyable experience and be able to relax for hours on the train.
“But because I couldn’t get to a toilet, I spent the night hoping for the morning to come.
“I would not have wanted to get up and try to find another toilet. I would also have been anxious about finding my way back to my room.
“If the toilets were not working on a plane, it would have to land.”
The passenger also said her friend “was not impressed” with how far she had had to walk to find a working toilet.
Ms Burke did not return by sleeper after the trip last November and flew on to a meeting in Dublin instead.
However, she said she would travel on the sleeper again. She had originally planned to book a seat, but was upgraded to a room when she told booking staff she was travelling with a guide dog.
Ms Burke was further upgraded to an accessible room with double bed when her friend said as they boarded that the twin room they had been allocated was too small for the three of them.
Graham Kelly, Serco’s guest experience director for Caledonian Sleeper, said: “We’re very sorry for this passenger’s experience on this occasion and have offered a full refund.“