The carmakers, which together are the world's fifth largest automakers by sales, sold 8.01 million vehicles, below their forecast of 8.2 million.
They expect sales to rise 1.5% in 2016, following a flat performance last year.
Both brands have faced stiff competition in recent years.
US and Japanese rivals have been regaining lost ground in the US, while demand in emerging markets and the world's biggest car market - China - has been cooling.
Meanwhile, a weaker yen has benefitted Japanese automakers, as a stronger Korean won and plunging currencies in markets such as Russia and Brazil has reduced the value of overseas sales for the South Korean carmakers.
In October, Hyundai reported that its quarterly profit fell to its lowest level in five years. Its shares plunged more than 12% last year.
The automakers sales target for this year marks the weakest sales growth in 10 years.
The economic slowdown in China, which is the group's largest market by volume, will continue to affect its growth this year, the company said.
Sales in the world's second largest economy fell in the first 11 months of last year.
South Korean automaker Hyundai Motor and its affiliate Kia Motors missed their global sales targets in 2015 for the first time since the financial crisis.