INDETERMINATE DOMAIN (IDD) genes encode a large family of putative transcription factors characterized by four different zinc finger motifs in a conserved arrangement. In Arabidopsis thaliana there are 16 IDD genes designated AtIDD1-AtIDD16. Microarray database expression resources show that AtIDD1 transcripts are present at high levels in dry seed and in response to abscisic acid. Transcripts present in dry seed at high levels have previously been shown to play roles in later stages of seed development or as provisions necessary for the resumption of metabolic activity following seed dormancy. Here I show that lines with constitutive expression of AtIDD1 have decreased and increased sensitivity to the phytohormones abscisic acid and gibberellic acid, respectively, when applied exogenously. Additionally, plants overexpressing AtIDD1 have altered mucilage extrusion and seed coat morphology. Altered seed coat morphology was also observed In constitutive AtIDD1 knock down lines. Therefore, these phenotypes could indicate that AtIDD1 plays a regulatory role in seeds during seed development and/or germination.