The index that assigns 1985 a base value of 100 fell from 71.6 in February to 70.2 in March, the Conference Board said.
The monthly Consumer Confidence Index is based on a survey of 5,000 households.
Lynn Franco, director of The Conference Board Consumer Research Center, said the decline "was due solely to a less favorable short-term outlook, while consumers' assessment of current conditions, on the other hand, continued to improve."
The firm's Present Situation Index rose from 46.4 to 51 and has reached its highest level in three and a half years.
"Despite this month's dip in confidence, consumers feel the economy is not losing momentum," Franco said in a statement.
In March, the number of respondents to the survey indicating economic conditions were "good" rose from 13.7 percent to 14.3 percent. The percentage of respondents indicating conditions were "bad" also rose, climbing one percentage point from 31.7 percent to 32.7 percent.
Similarly, compared to a month earlier, more consumers indicated jobs were easier to find, while more also indicated jobs were harder to find.
The percentage of respondents indicating jobs were "plentiful" rose from 7 percent to 9.4 percent while the number indicating jobs were "hard to get" rose from 38.6 percent to 41 percent.