The Whites duo face competition from Blackburn's Bradley Dack, West Brom's Dwight Gayle, Brentford's Neul Maupay and Sheffield Wednesday's Adam Reach.
Jansson and Cooper linked back up after an injury to Gaetano Berardi and have put in a string of strong performances together at the heart of Marcelo Bielsa's defence.
United conceded just four goals for the month of September as they earned one victory, two draws and fell to their first league defeat of the season.
You can cast your vote here for your player of the month.