Low-grade ultramafic nickel ores contain a high percentage of serpentine which, while having deleterious effects on processing, makes these ores a desirable feedstock for mineral carbonation. By conducting microwave pre-treatment, serpentine is shown to be converted to olivine, which increases the carbon uptake when compared to directly carbonating the untreated ultramafic nickel ore tailings. The effect of microwave pre-treatment and mineral carbonation of ultramafic nickel ore and the resultant impact on settling and filtration are explored. Results show by pre-treating the nickel ore for 15 min using microwave the settling and filtration rate of the ore slurry has been improved; also, the turbidity of the filtrate and moisture content of the filter cake has decreased. However, results also indicate that mineral carbonation hinders settling even though it improves the filtration rate.