BACKGROUND: The objective of this study is to compare the efficacy of the superparamagnetic iron oxide (SPIO)-guided and standard techniques for sentinel lymph node (SLN) detection in early breast cancer. Multiple inferiority trials have concluded the non-inferiority of SPIO to the conventional radioisotope technique, with or without blue dye, in detecting SLNs. PATIENTS AND METHODS: From July 2018 to August 2022, patients clinically diagnosed with node-negative invasive breast cancer were randomised into the study group (SPIO) and control group (radioisotope and blue dye). Patient data and disease characteristics were prospectively collected. SLN detection rates were compared between the two groups. RESULTS: A total of 282 patients undergoing 288 sentinel lymph node biopsy (SLNB) procedures were recruited, and 144 SLNB procedures were randomised into each group. The baseline patient and disease characteristics were comparable. SLN localisation failed in one patient in each group; the success rate of SLNB was 99.3%. The SPIO group demonstrated a higher mean number of SLNs harvested (3.3 versus 2.8, p = 0.039) and longer mean procedure duration (33.1 min versus 22.3 min, p = 0.01) than the control group did. In the study group, the concordance rates per patient and node were 99.3% and 94.6%, respectively. Sixty-seven positive SLNs were detected in 37 patients. The concordance rates per malignant SLNB procedure and positive SLN were 97.3% and 96.8%, respectively. CONCLUSION: Single-tracer SPIO-guided SLNB was non-inferior to the dual technique (radioisotope and blue dye) and could safely replace the gold standard for SLN mapping in early breast cancer.