Pending sales based on contracts signed -- contracts that will likely close by the end of March -- dropped 2.8 percent, putting the Pending Home Sales Index at 88.9, the trade group said.
The pending home sales index for December was revised downward to 91.5.
"While home buyers over the past two years have been exceptionally successful with historically low default rates, there is still an elevated level of shadow inventory of distressed homes from past lending mistakes that need to go through the system," NAR Chief Economist Lawrence Yun said in a statement.
"We should not expect the recovery to be in a straight upward path -- it will zigzag at times," he said.
The trade group said the pending home sales index fell 2.4 percent to 73.5 in January in the Northeast and 7.3 percent to 78 in the Midwest. In the South, the index rose 1.4 percent to 97.7. In the West, the index dropped 5.2 percent to 98.7.