Background This study aims to compare the marginal and internal fit of lithium disilicate endocrowns produced by conventional and/or digital impression and fabrication techniques. Methods Endocrown preparations were performed on 40 mandibular first molars. The teeth were divided into four groups (n = 10) based on the impression and fabrication technique; CON: conventional impression/manuel wax patterns/heat-pressed endocrowns, DCD: digital impression/CAD-CAM milled wax patterns/heat-pressed endocrowns, D3D: digital impression/3D printed resin patterns/heat-pressed endocrowns, DC: digital impression/digital design/CAD-CAM milled endocrowns. The marginal and internal fits of the endocrowns were measured by using the silicon replica technique and stereomicroscope with 57x magnification. The statistical analysis was carried out using the Kruskal-Wallis and paired two-sample t-tests. The significance level was set at p < 0.05. Results Marginal fit measurements revealed the following; CON: 111 mu m, DCD: 96 mu m, D3D: 91 mu m, and DC: 93 mu m. A statistically significant difference was found between the CON group and the other groups in the marginal fit measurement. Internal fit measurements revealed the following; CON: 120.75 mu m, DCD: 112 mu m, D3D: 114.88 mu m, and DC: 122 mu m. There was a statistically significant difference between the CON group and the DCD group in the internal fit measurement, while no significant difference observed between the other groups. Conclusions It is concluded that all endocrowns had a clinically acceptable marginal and internal fit. The use of digitally generated patterns, CAD-CAM milled or 3D printed, in the fabrication of endocrowns can be effective in producing restorations with improved marginal and internal adaptation. Clinical relevance The use of digital production methods can improve the marginal and internal adaptation of endocrown restorations.