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Aims Seminal vesicle invasion (SVI) in prostatic adenocarcinoma (PCa) is a high-risk feature associated with lymph node (LN) metastasis and adverse outcomes. However, the impact of SVI laterality on LN metastasis patterns, nodal burden, metastatic focus size and extranodal extension (ENE) remains underexplored.Methods We retrospectively analysed 225 PCa patients with SVI who underwent radical prostatectomy with LN dissection. Associations between SVI laterality, tumour grade, volume and nodal parameters were assessed using univariable and multivariable models.Results LN metastases were identified in 97 of 225 (43.1%) patients. Bilateral SVI was significantly associated with higher odds of LN metastasis (OR=2.01; p=0.040), nodal burden (IRR=1.89; p=0.004) and ENE (OR=3.76; p=0.013), independent of tumour volume, grade, age and race. Tumour volume and grade independently predicted LN metastasis (p=0.004 and p=0.048, respectively) and were associated with metastatic focus size (p=0.003 and p<0.001, respectively) and nodal burden (p=0.061 and p=0.045, respectively). LN spread mirrored SVI extent: unilateral SVI primarily led to ipsilateral involvement (22/36; 61.1%; p<0.001), while bilateral SVI increased the risk of bilateral spread (OR=3.81; p=0.003). White patients had significantly higher LN metastasis rates than black patients (p=0.010).Conclusions Bilateral SVI is a strong, independent predictor of LN metastasis, nodal burden and ENE. SVI laterality also correlates with LN spread patterns and could inform future risk stratification, though further validation is needed.