Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, has been demonstrated to exert antitumor activity in a variety of cancer cells. The underlying mechanism involves inhibition of cell cycle progression and induction of apoptosis. Besides, celecoxib has also been found to induce autophagy in some solid tumor cells. The aim of this study was to investigate the effect of celecoxib on cell proliferation in HL-60 human acute leukemia cells and to explore the potential mechanism. HL-60 cells were exposed to various concentrations of celecoxib and cell viability was evaluated by the MTT assay. Apoptosis was analyzed with flow cytometry and the amount of autophagosome was evaluated by LysoTracker probe labelling. The expression of apoptosis- and autophagy-related proteins was assayed by Western blot and LysoSensor probe labelling was used to detect the effect of celecoxib on the lysosomal functions. The results of this study indicated that celecoxib inhibited cell proliferation in a time- and dose-dependent fashion. The flow cytometry analysis showed that celecoxib induced apoptosis at low concentrations and mainly cell necrosis at high concentrations. The Western blot test confirmed the induction of apoptosis by the upregulation of apoptosis-related proteins cleaved caspase-3 and cleaved PARP. Furthermore, this study demonstrated that celecoxib prevented the autophagic flux by inhibiting lysosome function; the fluorescence intensity of the LysoTracker probe and the level of autophagy-related proteins LC3-II and p62 were increased, but the fluorescence intensity of the LysoSensor probe was weakened. These findings show that celecoxib is an autophagy suppresser and has antitumor effects in HL-60 cells by inducing cell apoptosis and necrosis.