The agency changed its outlook to negative from stable, while affirming its Baa2 long-term debt and Prime-2 commercial paper ratings.
"Talisman's negative rating outlook reflects the uncertain outcome of the portfolio transformation taking place under the company's strategic re-positioning," said Terry Marshall, Moody's senior vice-president.
"The company's capital productivity is weak and it is uncertain when a clear, profitable and sustainable organic growth profile will be evident."
Marshall added that "Talisman's leverage metrics are supportive of the Baa2 rating and we believe that the company has valuable assets that will be sold with associated, of not commensurate, debt reduction."
Moody's said its rating could be downgraded if, among other things, proceeds of asset sales are used for shareholder returns instead of debt reduction or re-investment. About $4.4 billion of rated long-term securities is affected, Moody's said.
Talisman has put as much as $3 billion in assets up for sale as it focuses its portfolio on two core operational areas: the Americas and Southeast Asia. On the block are offshore properties in the North Sea and a stake in a Colombian oil pipeline.
Activist investor Carl Icahn revealed earlier this week that he now controls six per cent of Talisman's stock. He said he could have conversations with the company's management about strategic alternatives, such as asset sales or a corporate restructuring, and may seek representation on its board of directors.
Talisman shares were up 11 cents at $12.84 in early-afternoon trading on the Toronto Stock Exchange.