The nodal status in breast cancer is a major prognostic factor in terms of survival. It also plays a role in the therapeutic decision-making process. Therefore, the evaluation of lymph node involvement in breast cancer is imperative in establishing a personalized treatment scheme. The sentinel lymph node procedure has proved successful for small breast tumors (T1–T2), limiting axillary lymphadenectomy and its side effects without changing overall survival. Even so, a substantial number of women must undergo axillary lymphadenectomy during a second surgery when the analysis of the sentinel node discloses major nodal involvement. Imaging can improve patient selection, especially those who appear eligible for immediate axillary lymphadenectomy. Ultrasound is able to depict morphological abnormalities in the lymph nodes such as cortical thickening, peripheral vascularization, hilar infiltration and loss of the kidney-shaped appearance of a normal node. When ultrasound is negative, the risk of massive nodal involvement is limited, thus allowing the oncologist to take an approach with the sentinel lymph node procedure. Magnetic resonance imaging (MRI) can also be useful in detecting pathological lymph nodes, particularly with diffusion-weighted MRI sequence.