Background <p>Breast cancer (BC) is the most common cancer in women. The majority of BC-related deaths result from metastasis and invasion. MicroRNA (miRNA) is a key regulatory factor that suppresses the expression of target genes. miR-1258 is considered one of the miRNAs significantly associated with BC, but its downstream target genes have not been fully defined. Our study aimed to elucidate the role of miR-1258 in breast cancer cell proliferation, migration, and invasion, identify its potential targets, and investigate its regulatory mechanisms.</p> Methods <p>miR-1258 expression in breast cancer was measured by Real‑time quantitative PCR. The effects of the Cell Counting Kit-8 method, the Transwell migration and invasion method on the behavior of tumor-related cells were studied. In addition, the interaction between miR-1258 and LARP4B in cancer was elucidated using dual-luciferase assays and Pearson correlation analysis.</p> Results <p>miR-1258 is significantly downregulated in breast cancer, whereas LARP4B is significantly upregulated; both are closely associated with patients’ TNM staging. miR-1258 is an independent prognostic factor; patients with low expression of miR-1258 exhibit shorter overall survival. In BC cells, overexpression of miR-1258 inhibits cell proliferation, migration, and invasion. LARP4B is a potential target gene of miR-1258, and silencing LARP4B inhibits cellular biological functions.</p> Conclusions <p>Low expression of miR-1258 may indicate poor prognosis in BC whilst its overexpression significantly inhibits proliferation, migration and invasion of BC cells. miR-1258 may inhibit BC progression by negatively regulating LARP4B.</p>