Alcoa's loss amounted to 13 cents per share. That compares with net income of $172 million, or 15 cents a share, a year ago.
Excluding $175 million in charges, Alcoa earned $32 million, or 3 cents per share.
Analysts surveyed by FactSet forecast break-even results on a per share basis. Such estimates typically exclude one-time items.
Revenue fell to $5.83 billion from $6.42 billion but still beat analysts' expectations.
Alcoa produces aluminum for a wide range of businesses, from automobiles to appliance makers and energy companies. It is the first company in the Dow Jones industrial average to report quarterly earnings, so investors often watch its results for signs of how earnings may unfold for other companies
Alcoa has been challenged by the global manufacturing slowdown that cut into demand from many of its customers. Aluminum production fell slightly and realized aluminum prices dropped 17 percent from a year ago.
The company lowered its 2012 global aluminum demand forecast to 6 percent from 7 percent, citing the economic slowdown in China. It said it is anticipating a slowdown across all major regions of the world for the rest of the year.
Alcoa released its results after the market closed. In regular trading Its shares rose 1 cent to end at $9.13. They added 6 cents in after-hours trading.