We experienced a case in which simultaneous weaning from sedation and mechanical ventilation were difficult because of instability of tracheal tube fixation that was caused by size mismatch between the trachea and the tube and by severe tracheal deviation. Irritative stimuli caused by the oral tracheal tube prevented conversion from deep sedation to light or no sedation. In this case, very early tracheostomy, which provided better tube fixation and successfully reduced the irritative stimuli to the trachea, was effective to help achieve discontinuation of sedation and facilitated successful weaning from mechanical ventilation. Eventually, the tracheostomy tube was successfully removed immediately after discontinuation of mechanical ventilation.