Yes, according to the Form 56 instructions, you will need to file one on a decedents return.
"Form 56 should be filed by a fiduciary (see Definitions below) to notify the IRS of the creation or termination of a fiduciary relationship under section 6903. For example, if you are acting as fiduciary for an individual, a decedent’s estate, or a trust, you may file Form 56"