The US Conference Board's consumer confidence index fell to 93.5 in August from a revised 97.4 in July.
This is the third consecutive decline in the consumer confidence index, which is now at its lowest level since last November. Confidence has fallen from a peak of 110.7 reached in March.
The decline in consumer confidence was unexpected as Wall Street analysts had forecast that consumer confidence would rise slightly to 97.4 in August.
June consumer confidence was revised to 97.4, up slightly from the initial estimate of 97.1.
The Present Situation Index fell to 92 in August from 99.4 in July. The Expectations Index fell to 94.5 from 96.1 in July.
Lynn Franco, director of The Conference Board's Consumer Research Center, said the "month-to-month decline in the Present Situation Index is a strong signal that business conditions have yet to turn around. It also suggests that consumer spending is not likely to gain momentum any time soon".