ArcelorMittal said profits increased 48% in the three months to the end of September compared with the same period a year earlier.
Third-quarter net profit was $1.35bn, up from $910M a year earlier.
Sales increased by 30% against a year ago, to $21.04bn.
But compared with the second quarter this year, earnings were down and the company warned of higher raw materials prices and slowing demand.
ArcelorMittal's chairman, Lakshmi Mittal, said the business had not matched expectations and that he was uncertain about the final three months of the year.
"Our outlook for the fourth quarter remains cautious as the expected higher input prices continue to work through the business and demand remains muted, though with some regional differences."
Steel spot prices have fallen but iron ore - one of the key raw materials for steel - prices have risen.
Steel demand has been growing although it remains below pre-crisis levels.
ArcelorMittal, headquartered are in Luxembourg, is responsible for around 6% of the world's steel output.
