It did not say how many jobs would be lost, but a spokesman told AAP the figure of 300 to 500 being floated in some media outlets was inaccurate.
The West Australian on Wednesday suggested that more than 150 roles would go.
The mine has a workforce of around 2,800 employees, making it one of the largest in Australia.
The move came after Hancock Iron Ore completed an annual operational review to identify how ore is mined, processed and blended across its operations.
"We continuously look at optimising our mine plan and the latest iteration extends our life of mine by 10 years, maximising how much of the orebody we can turn into product and reduce the amount of waste we mine," a spokesman said.
The result is that Hancock needs to reduce its mining activity at Roy Hill while maintaining its production rate above 63 million tonnes per annum for the Roy Hill system.
"We are working through the impact and will work with all affected," the spokesman said.
Earlier this week, Hancock Prospecting announced it had made a significant investment in Elon Musk's SpaceX during its global initial public offering.
The Wall Street Journal reported the stake was worth more than $US1 billion ($1.4 billion).
SpaceX shares have climbed 40 per cent in the three trading days since the company joined the US Nasdaq exchange and last closed at $US192.50, well above the issue price of $US135.
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