Two isostructural 9‐thiophenanthrene derivatives, 9‐dodecylthiophenanthrene, C26H34S, (I), and 9‐tetradecylthiophenanthrene, C28H38S, (II), are reported. They crystallize in the monoclinic space group P21/c with four molecules in a unit cell. The S—Cphenanthrene bonds are 1.767 (2) and 1.772 (4) Å and S—Calkyl bonds are 1.809 (2) and 1.804 (4) Å for (I) and (II), respectively. The bond angles at S are 104.04 (11) and 104.0 (2)° for (I) and (II), respectively.