It is well established that potassium (K+) is an essential nutrient for wheat (Triticum aestivumL.) growth and development. Several microRNAs (miRNAs), including miR166, are reportedly vital roles related to plant growth and stress responses. In this study, a K+starvation-responsive miRNA (miR166d) was identified, which showed increased expression in the roots of wheat seedlings exposed to low-K+stress. The overexpression of miR166d considerably increased the tolerance of transgenic Arabidopsis plants to K+deprivation treatment. Furthermore, disrupting miR166d expression via virus-induced gene silencing (VIGS) adversely affected wheat adaptation to low-K+stress. Additionally, miR166d directly targeted the calcium-dependent protein kinase 7-D gene (TaCPK7-D) in wheat. TheTaCPK7-Dgene expression was decreased in wheat seedling roots following K+starvation treatment. SilencingTaCPK7-Din wheat increased K+uptake under K+starvation. Moreover, we observed that the miR166d/TaCPK7-Dmodule could affect wheat tolerance to K+starvation stress by regulatingTaAKT1andTaHAK1expression. Taken together, our results indicate that miR166d is vital for K+uptake and K+starvation tolerance of wheat via regulation ofTaCPK7-D.