The Toronto-headquartered company produced 6.7 million silver-equivalent ounces (Ag-eq) during the three-month period, up from 4Moz Ag-eq a year earlier.
Production comprised 3.5Moz silver, 35,260oz gold, 4.4M pounds lead and 1.2Mlbs zinc.
Ag-eq output rose 31% from 5.1Moz in the June quarter.
"The record quarter was primarily due to the company receiving a full quarter of production from the San Dimas operation, along with increases in consolidated silver and gold grades of 19% and 35%, respectively," CEO Keith Neumeyer said.
"In fact, five of our six mines recorded higher production levels as a result of these significant grade improvements."
Consolidated silver grades in the quarter averaged 152g/t, compared to 127g/t in the previous period.
Neumeyer also announced a 20% cost-cutting programme across all areas of the business, citing prolonged weakness in the silver price. The company expected to have achieved its austerity measures by the March-quarter of 2019.
Silver output for the three quarters to date totalled 8.4Moz, or 15.8Moz of Ag-eq. The production was in line with full-year guidance of between 12-13.2Moz silver, or 20.5-22.6 Moz Ag-eq.
First Majestic closed in the black Monday, up 2.25% to C$8.19 a share, which gave the company a market valuation of about C$1.58 billion.