Project officer Cathie Kelly, 59, from Glasgow, told a court how she fell as she tried to make it back to the safety of her office.
She sued the owners of the building - an old Victorian school in Greenock - claiming they did not take sufficient care for her safety.
The Court Of Session, Edinburgh, heard how a nearby rubbish dump was a magnet for gulls that nested on the roof of the old school. They became aggressive when they had chicks.
Judge Paul Arthurson, QC, was told of people dashing in and out of the Ladyburn Business Centre in Pottery Street using umbrellas and how garages in the vicinity flew helium balloons to protect their cars from droppings.
Previously there had been patrols using owls and hawks to try to get rid of the menace, but these had stopped, said Mrs Kelly of Hayburn Lane, Hyndland.
In a written ruling, Judge Arthurson said: "I was particularly impressed with the evidence and demeanour of Mrs Kelly as she described the incident leading to her fall on the steps. This must have been truly terrifying for her."
But the judge said the crucial question was whether the attacking gull came from the Ladyburn Business Centre building.
Experts on gull behaviour told the court the birds were "free wild creatures" protecting their young, but where a chick was found was no indication as to where it had come from.
Judge Arthurson also ruled the landlords of the building, Riverside Inverclyde (Property Holdings Ltd), had carried out their responsibilities.
Mrs Kelly had told the court: "This gull came for me at full speed, wings outstretched, coming right for my face. It was screaming at me. I was terrified. I thought it was going for my face."
Later that afternoon someone noticed her crying and gave her a paracetamol but she was still in pain and had to go home early.
Her daughter took her to hospital that evening and the incident left her "shaken and distressed."
She was away from her work with CVS Inverclyde for two weeks.