The investment group, which owns 8.5 percent of Dell, said the deal "grossly undervalues the company," and said it would "avail itself of all options" to block the deal.
The business newspaper Barron's reported Saturday that Michael Dell's $3.7 billion stake in the company could triple in the next five years should the company go private. Shareholders are feeling shoved aside, Barron's reported.
Dell's board said this week going private would be the best way for the company to redesign itself, given the consumer movement away from personal computers as the market gravitates toward mobile devices.
The $24.4 billion deal valued Dell at $13.65 per share. Dell, however, is expected to earn a profit of $1.71 per share in 2013 -- one indication that the deal would be the cheapest privatization ever of a major company, Barron's said.
"This deal is so compellingly unfair to shareholders that I don't know where to begin," said Richard Pzena, chief investment officer at Pzena Investment Management, a major shareholder.
PIM estimates Dell's value at close to $25 per share.
Although shareholders would get a premium above the stock's recent average price before news of the possible deal broke, Dell's shares closed the week at $13.63 per share Friday.