Absolutely
"All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness, that the man of God may be complete, thoroughly equipped for every good work." - 2 Timothy 3:16
Paul wrote this when the only (completed) Scriptures were the Tanakh (sp?) (Hebrew) or the Septuagint (Greek), what we now know as the Old Testament. The New hadn't been completed yet, but that verse holds true for the NT as well.