The run of eight episodes is scheduled for Thursday on TNT. The new season is to begin Sept. 19 on ABC.
TNT this summer secured the exclusive off-network cable rights to the series from Disney-ABC Domestic Television.
The complete third season will be available on DVD beginning Sept. 20.
"Castle" is about Richard Castle, a famous mystery novelist and divorced father raising his teenage daughter and kept grounded by his Broadway diva mother. He finds inspiration in NYPD Detective Kate Beckett, a bright and aggressive homicide detective with a fascination for odd and offbeat cases stemming from the years-old unsolved homicide of her mother," TNT said in a synopsis.
It stars Nathan Fillion, Stana Katic, Tamala Jones, Jon Huertas, Seamus Dever and Molly Quinn.