The development of trichomes and root hairs in Arabidopsis provide useful models for the study of cell fate determination in plants. A common network of putative transcriptional regulators, including the small MYB proteins TRIPTYCHON (TRY) and CAPRICE (CPC), is known to influence the patterning of both cell types. Here, we used an activation tagging strategy to identify a new regulator, ENHANCER OF TRY AND CPC 1 (ETC1). The ETC1 sequence is similar to TRY and CPC, and ETC1 overexpression causes a reduction in trichome formation and excessive root hair production. The etc1 single mutant has no significant phenotype, but it enhances the effect of cpc and try on trichome and root hair development, which shows that ETC1 function is partially redundant with TRY and CPC. In addition, the etc1 try cpc triple mutant has novel phenotypes, revealing previously unrecognized roles for these regulators in epidermis development. An ETC1 promoter-reporter gene fusion is expressed in the developing trichome and non-hair cells, similar to the expression of TRY and CPC. These results suggest that ETC1, TRY, and CPC act in concert to repress the trichome cell fate in the shoot epidermis and the non-hair cell fate in the root epidermis.