The present study aims to characterize a cDNA encoding zebrafish thyroid hormone receptor $alpha{1}$ $(zTRalpha{1)}$ in order to investigate its possible role in the early stage of embryonic development. A mobility shift assay showed that $zTRalpha{1}$ overexpressed in COS7 cells specifically bound to thyroid hormone response element (TRE). In addition, the specific interaction of anti-rat $TRalpha{1}$ antibodies with $zTRalpha1$/TRE complexes demonstrated that the cDNA clone encoded zebrafish thyroid hormone receptor $alpha{1}$. Transient cotransfection assays showed that $zTRalpha{1}$ repressed the transcription which was induced by retinoic acid (RA), a well-characterized embryonic morphogen. These results suggest that zTRal may be involved in regulating the RA-induced gene transcription during early embryonic development.