Goldcorp, the world's third-biggest gold producer by market value, also said it would go ahead with plans to expand its Penasquito mine in Mexico and Musselwhite mine in Canada.
Production at Vancouver-based Goldcorp, which operates only in the Americas, plunged to 613,400 ounces in the quarter from 908,000 ounces in the year-ago period.
Goldcorp said it had expected gold production to decline mainly due to lower ore grades and a 10-day mill shutdown for maintenance at Penasquito. Operations resumed more slowly than had been expected.
The exhaustion of surface stockpiles at its Cerro Negro mine in Argentina, as well as a decision to lay off workers at the site, also reduced output.
All-in sustaining costs to produce an ounce of gold, an industry cost benchmark, rose to $1,067 from $853 a year ago in the quarter. Most other gold miners' costs have been falling.
Goldcorp reported a net loss of $78 million, or 9 cents a share, in the three months to end-June. That compared with net earnings of $392 million, or 47 cents per share, a year earlier.
Analysts, on average, had expected earnings of 3 cents a share, according to Thomson Reuters I/B/E/S.
Goldcorp affirmed its 2016 gold production forecast of 2.8 million to 3.1 million ounces at all-in sustaining costs of $850 to $925 per ounce.
(Reporting by Nicole Mordant in Vancouver; Editing by Chris Reese and Richard Chang)
