Peltz's experience in the packaged goods and consumer brands industries would add significant heft to P&G's board, Glass Lewis said in a statement released by Trian.
"We believe investors have been afforded ample cause to support Mr. Peltz's election at this time," the advisory firm said.
Activist hedge fund Trian disclosed a $3.5 billion (£2.58 billion) stake in P&G earlier this year and announced the nomination of its co-founder Peltz to the company's board. Trian's campaign represents the largest proxy fight ever against the more than $200 billion consumer products company.
P&G has argued that Peltz's plan to boost shareholder value by organising the company into three largely autonomous business units would result in higher costs, lower profits and another restructuring that could lead to a breakup of the company.
P&G said in a statement on Friday it was disappointed with Glass Lewis's conclusion.
Cincinnati-based P&G's annual shareholder meeting is scheduled for Oct. 10.
(Reporting by Gayathree Ganesan in Bengaluru; Editing by Sai Sachin Ravikumar)