MicroRNA (miR)-103a-3p has been shown to be involved in the development and progression of several types of cancer. However, the role of miR-103a-3p in thyroid cancer remains unclear. This study investigated the effects of miR-103a-3p on the biological characteristics of thyroid cancer cells and related mechanisms. In the present study, we found that the expression of miR-103a-3p was increased in thyroid cancer tissues compared to that in non-cancerous tissues. Additionally, the expression of miR-103a-3p in thyroid cancer cell lines (TPC-1, SW579, BHT101, K1) was markedly higher than that in the human thyroid cell line (Nthy-ori3-1). Silencing of miR-103a-3p obviously inhibited proliferation, migration, and invasion and promoted apoptosis of BHT101 cells. miR-103a-3p upregulation promoted the proliferation, migration, and invasion and inhibited apoptosis of K1 cells. Mechanistically, LATS1was identified as a functional target of miR-103a-3p and miR-103a-3p negatively regulated LATS1 expression. miR-103a-3p knockdown (or upregulation) partially reversed the effects of LATS1 knockdown (or overexpression) on proliferation, apoptosis, migration, and invasion of thyroid cancer cells. LATS1 knockdown inhibited the phosphorylation of YAP in BHT101 cells and pro moted the nuclear translocation of YAP. Whereas, miR-103a-3p downregulation reversed the inhibitory effect of LATS1 knockdown on Hippo signaling pathway. Moreover, overexpression of LATS1 induced YAP phospho rylation in K1 cells and inhibits nuclear translocation of YAP, and the upregulation of miR-103a-3p reversed this effect. Knockdown of miR-103a-3p inhibited tumor growth and progression in vivo. Taken together, knockdown of miR-103a-3p inhibits proliferation, migration, and invasion and promotes apoptosis of thyroid cancer cells through the Hippo signaling pathway by upregulating LATS1.