SummaryIn Arabidopsis, the tapetum plays important roles in anther development by providing enzymes for callose dissolution and materials for pollen‐wall formation, and by supplying nutrients for pollen development. Here, we report the identification and characterization of a male‐sterile mutant, defective in tapetal development and function 1 (tdf1), that exhibits irregular division and dysfunction of the tapetum. The TDF1 gene was characterized using a map‐based cloning strategy, and was confirmed by genetic complementation. It encodes a putative R2R3 MYB transcription factor, and is highly expressed in the tapetum, meiocytes and microspores during anther development. Callose staining and gene expression analysis suggested that TDF1 may be a key component in controlling callose dissolution. Semi‐quantitative and quantitative RT‐PCR analysis showed that TDF1 acts downstream of DYT1 and upstream of AMS and AtMYB103 in the transcriptional regulatory networks that regulate tapetal development. In conclusion, our results show that TDF1 plays a vital role in tapetal differentiation and function.