According to Official Guinness Records,
The oldest baseball player to hit a home run in a World Series game is David Ross (USA) who was aged 39 years 228 days when he hit a home run in Game 7, at Progressive Field, Cleveland, Ohio, USA, on 2 November 2016. Ross was playing for the Chicago Cubs, who beat the Cleveland Indians 4-3, making it their first win of the World Series in 108 years.
For a complete list of 2016 records, please visit 2016 Guinness Records in United States.