ISS and Glass Lewis both recommended that shareholders vote against proposals by MFE and Czech investor PPF at ProSieben's annual general meeting on April 30.
MFE, which holds nearly 30% of ProSieben's shares, wants the company to shed its e-commerce and dating businesses to focus on television, in a split that could eventually lead to a buyout approach for the German group's TV business.
Shares in ProSieben were down 4.6% at 1102 GMT, following the advisers' recommendation.
ProSieben's management and supervisory boards have rejected the proposed strategy shift, saying it would neither minimise debt or create value for investors.
ISS and Glass Lewis took a similar view, both recommending that shareholders back ProSieben's proposed candidates for the supervisory board and not those put forward by MFE and PPF.
Investor Amber Capital told Reuters last week that it would back the MFE plan.
ProSieben this week began the process of selling its online beauty retailer Flaconi and price comparison website Verivox.
MFE, which is controlled by the family of late Italian premier Silvio Berlusconi, welcomed this move in a statement on Friday.
"MFE is pleased to note that its efforts in encouraging the P7S1 management to re-focus on its core business are eventually coming to fruition," the media company said.
MFE said there was agreement on the general goal of switching focus to television, but also said "MFE and management appear to have different views as to urgency to act."
MFE is Italy's biggest commercial broadcaster and an advocate of pan-European consolidation in the sector.
(Reporting by Klaus Lauer, Writing by Rachel More, Editing by Friederike Heine and Jane Merriman)
