TmFeO₃ is known to have an orthorhombic structure characterized by the corner-linked FeO₆ octahedra in a three-dimensional network (space group Pnma). Thus, it is expected to be non-ferroelectric. In the present study, however, we have stabilized a hexagonal TmFeO₃ thin-film heterostructure by adopting hexagonal templates. In this way, we are able to artificially impose multiferroism on the epitaxially grown TmFeO₃ film below 120 K.