Ms Hosking objected to the multinational registering the trademark, on the basis that she was the first to register it and her customers were regularly confusing the two companies.
She claimed people would call her office on average once a day wanting repairs and advice on GPS units.
Major retailers were also mistakenly giving customers her business's contacts, instead of the GPS company's, according to Ms Hosking.
She also had to battle with people assuming she had copied the name TomTom. This assumption was particularly damaging for her company as she offered branding services.
In April, the Trademark Tribunal ruled that most of the confusion was low-level and much of the difficulty arose because Ms Hosking's company did not have a major reputation in New Zealand.
The tribunal considered misdirected mail and phone calls low-level issues and allowed the GPS company to trademark its name.
Ms Hosking appealed against the decision but was again unsuccessful.
In the decision released today, Justice Peter Woodhouse said it was "most unlikely" a large number of people would be confused by the two businesses.
"In my opinion, the prospective purchasers of the appellant's services are small, and coming from segments only of the public, not from the purchasing public as a whole," he said.
Some confusion appeared to be as a result of the difficulty contacting TomTom International's New Zealand branch, he said.
"I consider that if Tomtom International had provided readily accessible contact details and had been easier to reach, then much of the confusion described above would have fallen away, despite the similarities between the marks."
