Discrepancies between the dental midline and facial midline are often a primary complaint reported by patients seeking orthodontic treatment. The first step in the diagnosis of and treatment planning for all patients should be to identify the origin of these asymmetries. This case report presents a patient who had severe maxillary dental midline deviation. Thus, his maxillary left first premolar was extracted to make the midlines match and resolve the crowding using clear aligners. The treatment results showed that satisfactory therapeutic effects were achieved, with a balanced profile and stable occlusion. This case report outlines the diagnosis and orthodontic treatment of midline deviation. Compared to symmetrical extraction, asymmetrical extraction may be considered an optimal choice in some specific cases. Keywords: asymmetrical extraction, clear aligner, dental midline deviation