Andy Hadlington, 36, a computer game writer, witnessed the mysterious triangular-shaped object silently hovering above a residential neighbourhood in the West Country city on May 10.
In the video, a spinning grey object gliding around the village of Knowle - without making a sound, could be seen.
"It was the freakiest thing I have ever seen in my life. I was sitting in my office and saw it out of the corner of my eye," the Sun quoted Hadlington as saying.
"It was quite exciting - it sort of hovered past the houses. There was no sound. I ran downstairs and out of the garden to see where it went but I couldn't see anything.
"My fiancee was out at the time but I'm sure other people must have seen it. It was so clear," he added.
UFO experts have since been clambering to verify the sighting and are hoping to speak to more witnesses about the eerie episode.
Denis Plunkett, 78, of the British Flying Saucer Bureau, based in Winterbourne, near Bristol, was unable to comment on the video but said there were ways to verify its authenticity.
"There are ways to sort out good from bad. Firstly they are silent, there will be no noise," he said.
"They can also become invisible. They can go in and out of MoD radar. They can change speed, direction and height in seconds.
"The best thing is if there are multiple witnesses to the sighting. If more people saw this I'd be very interested," he added. (ANI)