"This depleted area of the ozone layer over the South Pole was slightly smaller than last year and generally continued the overall shrinking trend of recent years," the space agency said.
International efforts have been stepped up to remove the threat posed by the hole.
Nasa said the annual Antarctic ozone hole reached an average area of 23.2 million square kilometres between September 7 and October 13.
Ozone is a natural molecule made up of three oxygen atoms mostly found high above the Earth, where it acts as a shield against radiation and from the Sun's ultraviolet rays.
The causes of the hole were effectively tackled as a result of international co-operation known as the Montreal Protocol, an agreement struck in 1987.
The hole is known as the thinning of the ozone layer, first detected over Antarctica in the 1970s, that continued to deteriorate into the 1990s.
The cause of the damage was attributed by scientists to a number of man-made chemicals in the atmosphere, particularly chlorofluorocarbons (CFCs), which were used in sprays, foams, air conditioning and refrigerators.
Some businesses attempted to dismiss concerns over the ozone hole as nonsense.
“Over time, steady progress is being made and the hole is getting smaller,” said Paul Newman, chief scientist for Earth sciences atNasa’s Goddard Space Flight Centre in Greenbelt, Maryland.
“We see some wavering as weather changes and other factors make the numbers wiggle slightly from day to day and week to week.
“But overall, we see it decreasing through the past two decades. The elimination of ozone-depleting substances through the Montreal Protocol is shrinking the hole.”