Breast cancer has become the malignant disease with the highest morbidity and mortality among female cancer patients. The prognosis of metastatic breast cancer is very poor, and the therapeutic effects still need to be improved. The molecular mechanism of breast cancer has not been fully clarified. Bioinformatics analysis was used to find the differentially expressed gene that affects the occurrence and development of breast cancer. Furthermore, scratch assays, transwell assays, immunofluorescence and western blotting were used to determine the biological behaviour of breast cancer cells affected by DEPDC1B. The molecular mechanism was investigated by mass spectrometry analysis, coimmunoprecipitation and ubiquitin assays. Here, we found that DEPDC1B was highly expressed in breast cancer cells and tissues and was associated with lower overall survival (OS) in patients. We found that DEPDC1B interference significantly inhibited tumour invasion and migration in vitro and tumour metastasis in vivo. Mechanistically, DEPDC1B was first shown to activate the wnt/β-catenin signalling pathway as an oncogene in breast cancer cells. In addition, we also confirmed the interaction between DEPDC1B, USP5 and β-catenin. Then, we found that DEPDC1B mediates the deubiquitination of β-catenin via USP5, which promotes cell invasion and migration. Our findings provide new insights into the carcinogenic mechanism of DEPDC1B, suggesting that DEPDC1B can be considered a potential therapeutic target for breast cancer.