Background: We evaluated (1) the predictive accuracy and (2) multi-observer reliability of non-contrast CT markers of hematoma expansion (HE). Methods: In 124 patients with spontaneous intracerebral hemorrhage, two investigators documented the presence of six density (Barras density, hypodensity, black hole, swirl, blend, fluid level) and three shape (Barras shape, island, satellite) expansion markers, with discrepancies resolved by a third rater. We defined HE as any one of (1) >6 mL absolute or >33% relative growth of the intraparenchymal hematoma or (2) an absolute growth of >1 mL or new development of intraventricular hematoma. A subsample of 60 patients was used for the inter-observer reliability study in 13 raters. Seven raters participated in the intra-rater study. Results: The sensitivity of markers for HE varied between 4% (fluid level) and 78% (satellite), while specificity ranged from 37% (swirl) to 97% (black hole). Almost perfect inter-rater agreement was observed for the swirl (0.89) and fluid level (0.83) markers, while hypodensity (0.65) showed substantial agreement. Only the blend and fluid level markers achieved substantial intra-rater agreement (> 0.6) in all raters. Conclusions: Non-contrast CT markers of HE showed lower reliability and predictive accuracy than previously reported. Future studies should address means to improve NCCT-based HE prediction.