To develop thermoluminescent materials for neutron detection, 10B-enriched and 11B-enriched Ca2B2O5:Dy were prepared and their thermoluminescence (TL) properties were investigated after irradiation with X-rays, He ions and thermal neutrons. The TL of these materials was induced by X-rays and He ions and sensitivities to radiation are independent of the boron isotopes in the host materials. On the contrary, the TL intensity of the 10B-enriched sample was significantly higher than that of the 11B-enriched sample after irradiation with thermal neutrons. The high sensitivity to neutrons in the TL of the 10B-enriched sample is attributed to γ-rays and charged particles generated from 10B(n, α)7Li and 10B(n, α)7Li* reactions. In the neutron fluence range of the measurements (3.0 × 105 to 108 neutrons cm−2), the TL intensities attributed to 10B(n, α)7Li and 10B(n, α)7Li* reactions against thermal neutron fluence showed good linearity. In terms of detectable fluence, the new TL materials are more sensitive to neutrons than some existing Dy-containing TL materials.