The NO x storage and reduction (NSR) performance of low platinum (0.5 wt%) 0.5Pt–CoO x –15BaO/Al 2O 3 catalysts with varied Co loadings and calcination temperatures was studied to investigate the promotional effect of CoO x on the NSR catalysis. The NSR performance was tested under cyclic lean–rich conditions, and was evaluated in terms of NO x storage capacity (NSC) under the lean condition, the N 2 selectivity and the amount of nitrogen-containing products (namely, the NO x reduction capacity (NRC)) under the rich condition. For the catalysts calcined at 800 °C, addition of CoO x to the 0.5Pt–15BaO/Al 2O 3 catalyst enhanced the NSC but lowered significantly the NRC, which made the NRC/NSC ratios dropped significantly from 0.82 for the reference 0.5Pt–15BaO/Al 2O 3 catalyst to around 0.50 for the catalysts containing 1 and 5 wt% Co, and to 0.37 for the catalyst containing 10 wt% Co. Moreover, the N 2 selectivity remained at around 50% for the 0.5Pt–CoO x –15BaO/Al 2O 3 catalysts when the Co loading was kept low (0–5 wt%), and decreased significantly to 30% when the Co loading was 10 wt%. The calcination temperature of the 0.5Pt–CoO x –15BaO/Al 2O 3 sample containing 5 wt% Co was varied in the range of 350–800 °C to improve the NSR performance. The catalyst calcined at 550 °C was found to produce the highest NRC/NSC ratio (0.80) and N 2 selectivity (76.1%) under the rich condition. The maximum efficiency for NSR catalysis of this catalyst seemed to be associated with the amount of binary Pt–Co oxides.