TV Guide says that the project, How To Be A Gentleman, follows an uptight man who learns to make the most of his life with the help of an old school friend.
The show is said to be loosely based on the John Bridges book How To Be A Gentleman: A Contemporary Guide To Common Courtesy.
Hornsby is expected to star in, write and executive produce the show. Homeboys In Outer Space producer Ted Schachter is also working on the project.
Hornsby is currently writing and recurring in the FX comedy It's Always Sunny In Philadelphia. He has previously appeared in shows including Six Feet Under and Jake In Progress.