The jury ruled that the custom XML tagging features of Word 2003 and Word 2007 infringed on a patent from Toronto-based i4i.
A Microsoft representative said the company was "disappointed" by the verdict and would seek to have it reversed.
"We believe the evidence clearly demonstrated that we do not infringe and that the i4i patent is invalid," Microsoft spokesman David Bowermaster said in a statement. "We believe this award of damages is legally and factually unsupported, so we will ask the court to overturn the verdict."
Last month, in a separate infringement case brought by Uniloc, Microsoft was hit with a US$388 million verdict. The company said it would appeal that order.