According to Eurosport the Hammers are interested in signing the Mexican international.
West Ham who are targeting a top six finish this season have made bolstering their attacking line-up a top priority.
The report goes onto state that West Ham are preparing a three-year deal for the 27-year-old.
The United striker has also been linked with a move to Galatasaray, Besiktas and to the MLS side Orlando City.
Hernandez spent last season on loan at La Liga giants Real Madrid after falling out of favour with Manchester United boss Louis van Gaal.
The former Chivas striker’s future is unclear following a broken collarbone which will rule him out of the Gold Cup. The injury is expected to keep the Hernandez out of pre-season training for another three weeks.
Galatasaray booked a place in the Champions League group stages for the fourth consecutive season in the process.