Chile produced 464,572 mt of copper in September, down 5% from 489,170 mt a year earlier, according to figures released Wednesday by the country's statistics bureau INE.
INE attributed the drop to maintenance at a major mine and lower ore grades.
Chile is the world's largest copper producer.
Production during January-September totaled 4.281 million mt, up 1% from 4.239 million mt in the same period last year.
Production of molybdenum, a key byproduct in the country's largest copper mines, rose 40% in September to 3,819 mt from 2,727 mt a year earlier.
Molybdenum production between January and September totaled 35,563 mt, a year-on-year increase of 32.5% from 26,831 mt.
