A vehicular interior rearview mirror assembly includes a mirror casing and a reflective element, with the mirror casing adjustably supported at a mirror mount at an interior surface of the vehicle. The mirror casing includes a principal mirror casing portion and a pivotable mirror casing portion that is pivotable relative to the principal mirror casing portion. The reflective element is accommodated at the principal mirror casing portion. An upper portion of the pivotable mirror casing portion is integrally joined with the principal mirror casing portion at an upper region of the principal mirror casing portion. A spring element is coupled to the pivotable mirror casing portion and to a lower region of the principal mirror casing portion. The spring element flexes to adjust an angle of the principal mirror casing portion and the reflective element relative to the pivotable mirror casing portion of the mirror casing.