The review was a consequence of ''ongoing worsening market conditions and internationally uncompetitive power costs'' and would see the potential reduction of a small number of support roles, NZAS chief executive Gretta Stephens said in a statement.
The smelter employs about 800 employees and contractors.
In April, NZAS posted a $56 million after-tax profit for the 2014 year, its first profit in two years after losses of $49 million in 2012 and $18 million in 2013.
One of the major problems for NZAS was the price it paid for power and the transmission lines that feed electricity from the Manapouri power station to the smelter, she said.
Ms Stephens said electricity and transmission costs and ''historically depressed aluminium prices'' were still a significant pressure on the competitiveness of the business.
''Our team has worked tirelessly on cost savings and improvement programmes over the past three years but now we need to do more to ensure NZAS remains a viable business.
''We are continuously looking at ways to increase productivity to survive this bottom end of the commodity price cycle and at times this can affect workforce numbers.
''My immediate priority is to keep our employees safe and supported as we navigate our way through this tough time.''
