Nonfarm payrolls rose only 113,000, the Labor Department said on Friday. But with strong job gains in construction, cold weather probably was not a major factor in January.
The second straight month of weak hiring - marked by declines in retail, utilities, government, and education and health employment - could be a problem for the Federal Reserve, which is tapering its monthly bond-purchasing stimulus program.
December payrolls were raised only 1,000 to 75,000.
The data also comes on the heels of a report on Monday showing a surprise drop in factory activity to an eight-month low in January and could rattle investors, already nervous about slowing global growth.
Economists polled by Reuters had forecast payrolls increasing 185,000 last month and the unemployment rate to hold steady at 6.7 percent.
But there was a silver lining in the report. The unemployment rate dropped a tenth of a percentage point to 6.6 percent last month, the lowest since October 2008.
The household survey from which the jobless rate is derived showed gains in employment. In addition, more people came into the labor force, an encouraging sign for the labor market.
The participation rate, or the proportion of working-age Americans who have a job or are looking for one, increased to 63 percent from 62.8 percent in December, when it fell back to the more than 35-year low hit in October.
The unemployment rate is now flirting with the 6.5 percent level that Fed officials have said would trigger discussions over when to raise benchmark interest rates from near zero.
But policymakers have made it clear that rates will not rise any time soon even if the unemployment threshold is breached.
The private sector accounted for all the hiring in January. Government payrolls fell 29,000, the largest decline since October 2012.
Manufacturing employment increased 21,000, rising for a sixth month. Retail sector jobs fell 12,900 after strong increases in the prior months, the first decline since March.
Construction payrolls bounced back 48,000 after being depressed by the weather in December. It was the largest increase since December 2012.
Average hourly earnings rose five cents. The length of the workweek was steady at an average of 34.4 hours.