"I think the Yahoo-Starboard situation is a Yahoo-Starboard situation," Armstrong said in a "Squawk Box" interview.
He did say that "scale matters" when it comes to Internet properties, and speculation surrounding Yahoo highlights AOL's success. "We went to No. 4 in traffic in the U.S. this year," he said.
Starboard said Friday it acquired a "significant" stake in Yahoo, and urged the company to quickly "monetize" its windfall of billions of dollars from selling 140 million Alibaba shares in the Chinese company's blockbuster initial public offering earlier this month
A former activist investor in AOL, Starboard said a Yahoo-AOL merger could create up to $1 billion in "synergies" by reducing overlaps in online display advertising and other overhead costs.
"Our relationship with Starboard in the past has been around the alignment of the shareholders. And we went through our own proxy situation and had success in that for all the shareholders and all of our employees," Armstrong said. "So our focus since then has really been about driving AOL's strategy."
Armstrong and Yahoo CEO Marissa Mayer were top executives at Google before joining their respective companies in 2009 and 2012.