The credit card company posted adjusted earnings of $1.20 per share on revenue of $7.77 billion on Wednesday after the bell. Analysts expected the credit card company to report earnings of 97 cents a share on about $7.7 billion in revenue, according to a consensus estimate from Thomson Reuters.
"[American Express] continues to work its way through company-specific challenges, but its high return business model still benefits from the attractive relative growth of the payments/card industry," wrote Piper Jaffray analyst Jason Deleeuw, who has a "neutral" rating on the stock.
The company raised its 2016 guidance and now expects adjusted earnings between $5.90 and $6 a share, excluding restructuring charges, up from the previous projected range of $5.40 to $5.70 a share.
Shares rose to trade above $65 on Thursday morning. But Nomura analyst Bill Carcache lowered his price target to $56 for American Express shares, homing in on the company's marketing and promotion spending.
"[American Express] has always said that you have to spend money to make money," Carcache said.
The earnings report comes after Costco chose not to renew its partnership with American Express last year. AmEx shares have fallen about 13 percent over the past 12 months.
"We believe the majority of the upside this quarter was more due to overestimating the financial impact of Costco rather than any real fundamental improvement in the business," wrote Stifel analyst Christopher Brendler, who has a "hold" rating on the stock.
— Reporting by CNBC's Antonio José Vielma