Background Microscopic portal vein invasion (microPVI) and tumor multifocality are hepatocellular carcinoma (HCC) prognosis factors. To investigate whether microPVI and multifocality are directly related to each other. Methods We retrospectively analyzed the relationships between microPVI, multifocality, and maximum tumor diameter (MTD) in prospectively collected transplanted HCC patients. Results HCCs with 1, 2, or >= 3 foci had more microPVI in larger than in smaller HCCs, with microPVI being present in 52.24% of single large foci. Conversely, microPVI patients had similar percentages of single and multifocal lesions. A linear regression model of MTD, showed microPVI best associated with MTD, with 2.49 as coefficient, whereas multifocality had a 0.83 coefficient. A logistic regression model of microPVI showed significant association with tumor multifocality, especially for small HCCs. Trends for microPVI and multifocality in relation to MTD revealed that both increased with MTD but more significantly for microPVI. Survival was similar in patients with small HCCs, with or without microPVI, but was significantly worse in microPVI patients with larger HCCs. No patient survival differences were found in relation to focality. Conclusions MTD had stronger associations with microPVI than with multifocality. microPVI was associated with worse survival in patients with large HCCs, but survival was not impacted by number of tumor foci. microPVI and multifocality appear weakly related, having different behavior in relation to MTD and survival.