The credit card issuer's net income grew one per cent to $1.34 billion, or $1.15 per share, in the second quarter. Revenue jumped 5 per cent to $8 billion.
Wall Street was expecting a profit of $1.10 per share and revenue of $8 billion.
CEO Kenneth Chenault said spending among the company's consumer, small business and corporate card members was slower than in recent quarters, but faster than at its competitors.
Amex's stock was off 54 cents at $57.75 in after-hours trading.
American Express has been doing well after the recession as affluent shoppers spent freely. That's because Amex cardholders are about a third more affluent than other credit cardholders.
Unlike Visa and MasterCard, which only process transactions, American Express issues its own cards. When cardholders charge more on their Amex cards, the company earns even more in interest income and a variety of fees.
However, the slowdown in Europe and Asia seems to have curbed spending among its customers.
Its international revenues fell 4 per cent to $1.3 billion. Even after adjusting for the strength of the dollar, revenue in that division rose only 2 per cent.
The revenue that Amex collects from other countries fell after being converted back into dollars. Barclays Capital analyst Mark DeVries said in a report to clients that the euro's value against the dollar declined 11 per cent, and the British pound declined 3 per cent in the quarter.
Spain and Italy were the hardest hit markets, a sign that even the wealthiest in those countries are worried. Customers in Spain, where banks are teetering, spent 5 per cent less. In Italy, Amex revenue was flat. However, revenue grew 4 per cent in U.K. and 5 per cent in Germany, according to American Express chief financial officer Daniel T. Henry, who made a presentation to analysts on Wednesday evening after releasing earnings.
The U.S. stock market also swung wildly in the quarter. The Standard & Poor's 500 index fell 3.3 per cent and the Nasdaq 5 per cent.
Amex's results provide investors insight into how the affluent consumer is doing. According to Citi Research the affluent account for about nine-tenths of stock owners in the country and are the most impacted by stock market volatility. These same high-income consumers also account for about half of all spending in the U.S.
Amex's growth slowed in the U.S. Compared to the 35 per cent income growth in the first three months of the year, Amex's income in the second quarter rose 8 per cent, and revenue grew by 7 per cent in the U.S.