Cellulose synthase (CesA) plays a major regulatory role in the cellulose synthesis pathway in plants and is an important factor in controlling wood fiber quality and yield. In this study, two cellulose synthase genes, AmCesA1 and AmCesA2, were cloned from Acacia mangium using transcriptome de novo sequencing analysis and RACE. In silico analysis revealed that AmCesA1 cDNA was 3793 bp in size, had a 3249 bp ORF, and encoded a 1082 amino acid protein; AmCesA2 cDNA was 3743 bp in size, had a 3228 bp ORF, and encoded a 1075 amino acid protein. AmCesA1 was determined to have six transmembrane regions, and AmCesA2 was determined to have eight transmembrane regions. Cluster analysis showed that AmCesA1 had high degrees of similarity with Glycine max GmCesA1 and Arachis duranensis AdCesA1. AmCesA2 had high degrees of similarity with Leucaena leucocephala LlCesA7 and LlCesA8. Southern blot analysis showed that multiple copies of AmCesA1 were present in the Acacia mangium genome, but only a single copy of AmCesA2 was present. Real-time RT-PCR showed that both genes were widely expressed in roots, stems, and leaves, but AmCesA2 was more highly expressed in stems. The two genes responded to GA3, 6-BA, and MeJA treatments, and the response to GA3 was relatively strong. Here, we presume that the two genes are involved in the formation of primary cell walls and that AmCesA2 is also involved in the formation of secondary cell walls. The expression of both genes was upregulated under different hormone treatments, which indicated that the two genes positively regulate the hormone response.