Breast　cancer　is　the　most　common　malignant　tumor　in　women　worldwide.　To　explore　the　role　of　DACT2　in　breast　cancer,　5　cell　lines　and　153　cases　of　primary　cancer　were　studied.　The　expression　of　DACT2　was　detected　in　BT474,　MDA-MB-231　and　BT549　cells,　while　no　expression　was　found　in　MDA-MB-468　and　HBL100　cells.　Complete　methylation　of　DACT2　was　found　in　MDA-MB-468　and　HBL100　cells,　partial　methylation　was　observed　in　BT474　and　BT549　cells,　and　no　methylation　was　detected　in　MDA-MB-231　cells.　Restoration　of　DACT2　expression　was　induced　by　5-Aza　in　MDA-MB-468　and　HBL100　cells.　DACT2　was　methylated　in　49.7%　(76/153)　of　primary　breast　cancer　samples.　Methylation　of　DACT2　was　significantly　associated　with　tumor　size　(P　＜　0.05).　Reduced　DACT2　expression　was　significantly　associated　with　promoter　region　methylation　in　primary　breast　cancer　(P　＜　0.05).　DACT2　suppressed　breast　cancer　cell　growth　and　induced　G1/S　phase　arrest　in　breast　cancer　cells.　DACT2　inhibited　Wnt/beta-catenin　signaling　in　human　breast　cancer　cells　and　suppressed　breast　cancer　cell　tumor　growth　in　xenograft　mice.　In　conclusion,　our　results　demonstrate　that　DACT2　is　frequently　methylated　in　human　breast　cancer,　methylation　of　DACT2　activates　Wnt　signaling,　and　DACT2　suppresses　breast　cancer　cell　growth　both　in　vitro　and　in　vivo.