The No.3 automaker in the United States by sales said it sold 156,021 vehicles in January, down from 167,056 vehicles a year earlier. Camry sales fell 3.4 percent, while Prius sales slumped 57 percent, the company said.
Auto industry consultants J.D. Power and LMC Automotive forecast January auto sales to decline about 1 percent from the same month in 2018, partly due to uncertainty over the recent government shutdown.
The auto consultants also forecast total light vehicle sales this year to fall 1.9 percent to about 17 million units, compared with 2018.
However, major automakers are bullish about 2019 sales even as economists warned that rising interest rates may discourage consumers from buying cars this year.
Bloomberg, however, reported late on Friday that Ford's sales rose 7 percent, while GM's fell 7 percent in January, citing people familiar with the matter. GM declined to comment, while Ford was unavailable for comment.
"In spite of some frigid January weather, we remain bullish on 2019 given the continued underlying strength of the U.S. economy," Reid Bigland, Fiat's U.S. head of sales, said.
Fiat said it sold 136,082 vehicles last month, compared with 132,803 units for the same period a year earlier.
Sales of Ram pickup trucks surged 24 percent to 39,649 vehicles in January, compared with the same period a year earlier.