Introduction Breast-conserving therapy (BCT) aims to achieve complete tumour excision while preserving healthy tissue. Trident is an intra-operative X-ray system that allows real-time margin assessment. We hypothesised that the introduction of Trident would reduce re-excision rates following BCT. Our aim was to evaluate the impact of Trident on re-excision rates following BCT and to identify operative and tumour-related factors associated with improved effectiveness. Methods BCT excisions performed between 2016 and 2023 were retrospectively analysed. Cases using Trident formed the intervention group (n=249), while cases without intra-operative imaging served as controls (n=272). Benign lesions, duct excisions, and mastectomies were excluded. Data collected included patient demographics, neoadjuvant therapy, operation type, localisation method, tumour size, cavity shave excision, histopathology including margin and cavity shave status, and return to theatre for re-excision or completion mastectomy. Categorical variables were analysed using Fisher’s exact test with significance set at p<0.05. Results Overall re-excision rates were lower in the Trident group compared with controls (19% vs 26%), although this did not reach statistical significance (p=0.09). Trident was associated with a significantly reduced re-excision rate for simple wide local excisions (16% vs 25%, p=0.046). Trident use was associated with higher rates of cavity shaves (65% vs 48%, p<0.001), which was itself associated with reduced re-excision rates (19% vs 31%, p=0.02). Trident-guided cavity shaves demonstrated higher rates of positive shave margins (25% vs 12%, p=0.006) and lower rates of alternative margin positivity (7% vs 16%, p=0.02). DCIS was associated with higher re-excision rates than other histological subtypes (40% vs 19%, p<0.001). Conclusions Trident was associated with reduced re-excision rates in selected BCT procedures and appeared to improve the accuracy of cavity shave assessment.