Background: Use of radiocolloids for sentinel lymph node (SLN) detection in breast cancer (BC) offers the advantage of utilizing single-photon emission computed tomography/computed tomography (SPECT/CT). This study explored whether SPECT/CT findings can predict pathological axillary lymph node (ALN) metastasis. Methods: A consecutive series of patients with invasive BC (clinical stage, T1-3, N0, and M0) who underwent SLN biopsy (SLNB) using SPECT/CT between January 2011 and December 2016 were included. SLN detection, location, and number on SPECT/CT, number of excised SLNs, and clinical and pathological characteristics were analyzed in relation to pathological ALN metastasis. Results: Data from 408 patients (412 cases) with BC were analyzed. Patient age ranged from 28 to 93 years (mean: 59). SPECT/CT identified one to four SLNs (mean: 1.3) in 407 cases (98.8%) and no SLNs in 5 cases (1.2%). Of the 407 cases with at least one identified SLN, SLNs were solely in level I of the axilla in 394 cases (96.8%), both in and outside level I in 12 (2.9%), and solely outside of level I in 1 (0.2%). The number of ALNs removed via SLNB ranged from one to eight (mean: 2.0). SPECT/CT findings, including absence of SLN detection (P<0.001), SLN locations outside of axillary level I (P<0.001), and an increased number of SLNs (P=0.034), as well as removal of ≥3 SLNs (P=0.028), were significantly correlated with pathological ALN metastasis. Conclusions: SLNB with SPECT/CT yields useful information on pathological ALN metastasis in BC patients.