They found that the vacancy rate in the city's "prime retail area" fell from almost 20% in 2014 to 12.5% in 2015.
The agency said this was the largest fall in vacancies since 2011.
A rates revaluation, which cut the cost of occupying a shop on Royal Avenue/ Donegall Place, was part of the reason for the improvement.
That area of the city has seen a wave of new occupiers including DW Sports, Gap and Skechers.
Across Northern Ireland vacancies were down from 17.1% to 14.6%.
Lisney said the improvement also extended to out-of-town locations.
The agency predicts that continued occupier demand will lead to an increase in rents in prime locations over the next year.
The number of empty shops in central Belfast fell sharply in 2015, according to research by Lisney, the commercial property agents.