The CO₂ sorption properties of sodium hafnium oxide (Na₂HfO₃) were investigated in this study. Na₂HfO₃ was synthesized by solid-state synthesis using Na₂CO₃ and HfO₂ as starting materials. The solid-state synthesized Na₂HfO₃ appeared structurally similar to other mixed metal oxides such as Na₂ZrO_3, but stacking disorder appeared to be common in Na₂HfO₃. The synthesis conditions, including the Na : Hf ratio (between 0.5 and 1.5 : 1), synthesis temperature, time and heating rate, were investigated to optimize CO₂ sorption properties of Na₂HfO₃. The Na₂HfO₃ sorbent showed comparable CO₂ uptake capacity, reaction rate and excellent cycling stability compared to other metal oxide sorbents. Na₂HfO₃ with Na : Hf = 1 : 1 and 1.25 : 1 showed the highest CO₂ uptake among all Na₂HfO₃ samples obtained, with a CO₂ uptake capacity of around 15 wt% (at 650–800 °C). The CO₂ uptake rate of NHO-1 and NHO-1.25 was fast with over 80% of the equilibrium uptake reached within 250 s. Na₂HfO₃ remained stable even after 100 cycles with less than 3% difference in the CO₂ uptake capacity between the 1st and 100th cycles. We performed kinetic analysis on the CO₂ sorption data and found that the Avrami–Erofeev model fitted the kinetic data best among the kinetic models used. Apart from sorbent optimization, we showed that 3D-printing of Na₂HfO₃ : HfO₂ mixtures can be used to produce structured Na₂HfO₃ sorbents with a slightly improved CO₂ uptake rate and the same CO₂ uptake capacity as the powder-based solid-state synthesized Na₂HfO₃ sorbent.