Powdery mildew is an apple disease caused by the obligate trophic fungusPodosphaera leucotricha.Basic helix–loop–helix (bHLH) transcription factors play important roles in plant development and stress responses, and they have been widely studied in model plants such asArabidopsis thaliana.However, their role in the stress response of perennial fruit trees remains unclear. Here, we investigated the role ofMdbHLH093in the powdery mildew of apples. The expression ofMdbHLH093was significantly induced during the infection of apples with powdery mildew, and the allogenic overexpression ofMdbHLH093inA. thalianaenhanced the resistance to powdery mildew by increasing the accumulation of hydrogen peroxide (H2O2) and activating the salicylic acid (SA) signaling pathway. The transient overexpression ofMdbHLH093in apple leaves increased the resistance to powdery mildew. Conversely, whenMdbHLH093expression was silenced, the sensitivity of apple leaves to powdery mildew was increased. The physical interaction between MdbHLH093 and MdMYB116 was demonstrated by yeast two-hybrid, bi-molecular fluorescence complementation, and split luciferase experiments. Collectively, these results indicate that MdbHLH093 interacts with MdMYB116 to improve apple resistance to powdery mildew by increasing the accumulation of H2O2and activating the SA signaling pathway, as well as by providing a new candidate gene for resistance molecular breeding.