Tbx1 is one of the genes mapped within the del22q11 locus in human. The homozygous mutation of Tbx1 in mice and zebrafish both display the phenotypic complex that closely resembles those seen in DiGeorge syndrome (DGS) patients. Therefore, Tbx1 currently represents the major candidate gene for DGS. Regarding the activity of Tbx1 as a transcription factor, the interaction with the other cardiac transcription factors in vertebrate development, have not been elucidated. Morpholino antisense technology is a reliable gene knockdown method in zebrafish and can prevent translation of the target gene. In this paper, Tbx1 specific morpholino was used to reduce the amount of Tbx1 in zebrafish. Whole-mount in situ hybridization was used to monitor the expressions of Tbx20, Bmp2b and Nppa. It is showed that decreased expression of Tbx20 in the heart in Tbx1 morphant embryos; this result raised a possibility that Tbx1 may regulate Tbx20 expression in the heart directly or indirectly. In particular, the loss of Tbx1 function led to a dramatic down-regulation of Bmp2b in the heart and pharyngeal pouches. Interestingly, the expression of Nppa was significantly elevated in the ventricle, although atrial expression appeared normal. Conclusively Tbx1 is important for the expression of several key regulators of cardiac development, and thus we propose that the loss of Tbx1 affects heart development via a breakdown of transcription factor networks.