TRUE, Because
Definition of decidable language: A language is decidable iff it is Turing recognizable and co-Turing recognizable.
In other words, a language is decidable exactly when both it and its complement are Turing-recognizable.
Then, During the complementation of decidable language, the Turing recognizable will be co-Turing recognizable and Turing co-recognizable will be Turing recognizable.
thats why , after complementation, language will also follow the definition of decidable languages.
so, complement of every Turing decidable is Turing decidable.