The europium doped calcium bismuth borates, CaBi₂B₄O₁₀:xEu³⁺ (x = 0–0.3), were prepared using high-temperature solid state synthesis. The crystal structure of the CaBi₂B₄O₁₀ was solved and refined from single crystal X-ray diffraction data to R₁ = 0.029. The CaBi₂B₄O₁₀ crystallizes in triclinic space group P1‾, a = 6.6665 (1), b = 6.8277 (1), c = 9.5478 (1) Å, α = 94.2420 (8)°, β = 108.5210 (8)°, γ = 101.2840 (8)°, V = 399.76 (1), Z = 2. This compound is isotypical to SrBi₂B₄O₁₀. Crystal structure contains [B₄O₉]^6– isolated tetraborate groups (4 B:3Δ□: ˂2Δ□˃Δ), Bi–O chains and interstitial Sr atoms. Tetraborate group consists of the triborate ring [B₃O₇]^5– and branched BO₃ triangle. Thermal expansion of CaBi₂B₄O₁₀ was studied by powder HTXRD. The thermal expansion is highly anisotropic (α₁₁ = 14.9 (7), α₂₂ = 2.8 (1), α₃₃ = 7.2 (4), α_V = 25 (1) × 10⁻⁶ °C⁻¹ at 25 °C). Maximal thermal expansion occurs between the planes of triborate ring and branched BO₃ triangle. These solid solutions show an efficient red emission (λ_max = 611 nm) when excited by UV-light (λ_ex = 392 nm). The optimal europium doping concentration in CaBi₂B₄O₁₀ host was found to be 10 at.% due to the area of miscibility of CaBi_2-xEu_xB₄O₁₀ (x = 0–0.225) solid solutions.