Chemical composition, crystal structure, and Raman spectrum have been investigated for the Na-rich kihlmanite-(Ce). Chemical composition of this mineral: Na ₂ O 4.83, SiO ₂ 9.76, CaO 0.94, TiO ₂ 11.74, Nb ₂ O ₅ 1.83, La ₂ O ₃ 10.63, Ce ₂ O ₃ 26.22, Pr ₂ O ₃ 2.23, Nd ₂ O ₃ 9.00, Sm ₂ O ₃ 1.30, CO ₂ 14.40, H ₂ O 6.00, corresponds to empirical formula: (Na _0.95 Ca _0.11 ) _1.06 (Ce _0.98 La _0.40 Nd _0.33 Pr _0.08 Sm _0.05 ) _1.85 (Ti _0.91 Nb _0.08 ) _0.99 O ₂ [Si _1.00 O ₄ ] {(HCO ₃ ) _1.24 (CO ₃ ) _0.76 } ₂ H ₂ O. Raman spectrum contains following lines: 850, 722, (v ₃ , Si-O) 564, 610, 424 (v ₂ , v ₄ , Si-O), 1069, 919, 964 (v ₁ , CO ₃ , HCO ₃ ), 675 (v ₄ , CO ₃ ), 388 (CaO ₆ , NaO ₆ ), 290 (TiO ₆ ) cm ^-1 . Crystal structure is refined in the space group P1 (a = 5.0005(3), b = = 7.5273(6), c = 15.3344(16) A, α = 101.950(8), β = 92.938(7), γ = 109.323(7)°) up to the value of crystallographic repeatability factor R ₁ = 0.054 for 1842 independent reflections (|F _o | > 4σF). Obtained crystal-chemical formula may be written as following: (Na _1.10 Ca _0.11 ) _1.21 Ce _2.00 (Ti _0.77 Nb _0.23 ) _1.00 O _2.00 [Si _1.00 O _4.00 ]{(CO ₃ ) _1.55 (HCO ₃ ) _0.45 } _2.00 H ₂ O _1.16 . Na atoms occupy in the structure three independent positions: Na(l), Na(2) and Na(3). The presence of additional sodium site, relatively to the standard kihlmanite-(Ce), enforces chemical bonds between «tundrite» layers due to decrease of the unit cell parameter c by ∼ 0.1 A. Occurrence of sodium in the kihlmanite-(Ce) structure by the scheme: + HOC ₃ ^- Na ⁺ CO ₃ ^2- leads to the dominance of CO ₃ ^2- groups in hydrocarbonate position.