The miner, which keeps its books in U.S. dollars, said Wednesday it earned $71.9 million, or 12 cents per diluted share, for the quarter ended June 30.
That compared with a profit $142 million or 30 cents per share a year ago.
First Quantum said revenue came in at $869.3 million for the quarter, up from $722.3 million year over year.
On average, analysts had been expecting earnings of $116.86 million, or 23 cents a share, on revenue of $937.17 million, according to Thomson Reuters.
Total copper production was up 43 per cent compared with a year ago, while total nickel production improved by 33 per cent.
Total gold production increased 46 per cent over the second quarter of 2012.
"Good cost control combined with the addition of the acquired operations to our asset base effectively reduced our production cost of both copper and nickel," said chief executive and chairman Philip Pascall in a statement.
"This low cost profile enables First Quantum to be profitable, and to generate healthy cash flows, even in low metal price environments.
The company said the increase in production was helped by a recent takeover of Inmet Mining Corp., which runs the Cobre Panama project in Peru.
The Vancouver-based metals and mining company operates seven mines and five development projects worldwide. It produces copper, nickel, gold, zinc and platinum group metals.