Objectives: This study was performed to screen target-specific inhibitors of ${eta}$-catenin/TCF signaling whose functional activation plays an important role in early events in carcinogenesis. Methods: To investigate the activation or suppression of ${eta}$-catenin/TCF transcription, we established a transiently transfected cell line with a constitutively active ${eta}$-catenin mutant gene whose product is not degraded. This cell line was also co-transfected with luciferase reporter gene constructs containing either an optimized (TOPflash) or mutant (FOPflash) TCF-binding element. We investigated cytotoxic effects using a 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium salt (MTS) assay. To find effective inhibitors of ${eta}$-catenin/TCF signaling from medicinal herbs, the crude extracts of 99 types of medicinal herbs were screened using a luciferase assay system in HEK-293 and SH-SY5y cells. Results: At a concentration of $50{mu}g$/ml, extracts of Angelica koreanae radix, Cannabis sativa semen, Ephedrae intermedia Schrenk radix, and Vitis rotundifolia fruit showed the following inhibitory effects on ${eta}$-catenin/TCF signaling: $40{pm}5.6%$, $23{pm}6.1%$, $8{pm}5.1%$, and $22{pm}9.8%$ in ${eta}$-catenin-activated HEK-293 cells and $9{pm}4.7%$, $39{pm}8.1%$, $39{pm}6.4%$, and $42{pm}10.1%$ in ${eta}$-catenin-activated SH-SY5y cells, respectively. Crude extracts of E. radix were isolated by silica gel column chromatography, and two non-polar fractions of these extracts showed inhibitory effects on ${eta}$-catenin/TCF signaling. Conclusions: In this study, we established a transiently transfected cell line as a screening system and found that various medicinal herb extracts had inhibitory effects on ${eta}$signaling.