The multiple cytoprotective mechanisms of heme oxygenase (HO)-1 make it a promising therapeutic target. This study investigated whether the selective cyclooxygenase (COX)-2 inhibitor, celecoxib, can upregulate HO-1 expression. Murine J774 macrophages and rat aortic vascular smooth muscle cells (VSMCs) were used to study the effect of celecoxib on HO-1 expression. A signal transduction pathway involving reactive oxygen species (ROS) was also investigated. We found that celecoxib can upregulate HO-1 gene and protein expressions in J774 macrophages and VSMCs. This effect was not diminished by prostaglandin E(2) or 15dPGJ(2), while it was additive to hypoxia-induced HO-1 expression, suggesting an event independent of COX-2 activity or hypoxia-inducible factor-1α. Moreover, celecoxib activated ERK, p38, Akt, and Nrf2 as well as increased ROS production. All these events contributed to the increase in the expression of HO-1 caused by celecoxib. In this study, we also, for the first time, demonstrated that AMP-activated protein kinase (AMPK) can mediate HO-1 expression via the downstream activation of p38 and Akt. However, the HO-1-inducing actions of celecoxib and hypoxia were not associated with AMPK. This study demonstrates a COX-2-independent action of celecoxib in upregulating HO-1 in macrophages and VSMCs. This action is dependent on ROS, Akt, ERK, p38, and Nrf2 activation. These findings provide new insights into the action mechanism of celecoxib with broad implications for anti-inflammation therapy.