Described herein is a safety device against false maneuvers for sliding window and door frames, including an arrest designed to prevent displacement of the catch of the mobile frame of the window or door frame from its inoperative position to the operative position of engagement with a corresponding striker of the fixed frame, in the condition for opening the window or door frame. The arrest with the corresponding thrust member, adjustable in a direction parallel to the direction of displacement of the arrest, is carried by a slide that is adjustable in a direction orthogonal to the direction of displacement of the arrest.