The 23-year-old will miss their FA Cup third-round tie with Norwich and their next two games after he saw red for an alleged elbow on Greg Cunningham in the 11th minute of the 4-2 defeat.
The appeal did mean that Tomlin could play in their New Year's Day clash, which Posh won 2-1 against Barnsley.
Tomlin, who joined the club from Rushden in 2010, has scored eight goals this season for the Championship strugglers.
- Sports & Recreation
- Greg Cunningham