The smelter has been uneconomic since the former Xstrata-owned Brunswick mine closed in 2013.
Zinc and lead assets head Chris Eskdale said the company had "thoroughly assessed all options" but ultimately concluded "the smelter is simply not sustainable".
He said the closure came regardless of the recent labour dispute.
About 280 workers from the Brunswick smelter in Belledune, members of USW Local 7085, have been locked out of their jobs by Glencore since April 24. The workers say the Swiss-based multinational is demanding concessions that include "attacks on the workers' health and safety standards and union representation".
Glencore said it would provide pension, severance and outplacement support services for all employees as part of closure settlements yet to be agreed on. The company would also seek potential relocation opportunities at its mining and metallurgical operations in other provinces and countries, which might be available to Brunswick smelter workers.
The company plans to retain "a small number" of employees on site for monitoring, water treatment and closure projects "in the months ahead".
The Brunswick smelter opened in 1966 as part of the Brunswick No.12 development, underpinned by the largest deposit in the Bathurst base metals camp and was one of the largest underground zinc mines in the world well into the late 1990s.
The Brunswick Local 7085 website advised the committee would meet this Friday "to make a game plan" and would meet the company on Monday morning to discuss the closure.