Some Acacia species are well domesticated in some regions for supplying raw material for industries. Achievement in wood technology and tree breeding had made the product diversification from the Acacias are becoming more attractive. As a fundamental component, however, the information in wood anatomical structure of the Acacias was still limited. This study is aimed to observe wood anatomical structures of four tropical Acacias obtained from a tree improvement program. The wood samples were collected from three years age of four Acacias: Acacia mangium, Acacia auriculiformis, and their hybrids (A. mangium x A. auriculiformis and A. auriculiformis x A. mangium) planted in Acacia hybrid seed orchard. The wood anatomical structures were observed including some macroscopic and microscopic features. The results showed that wood anatomical structures varied among the four Acacias. Some macroscopic features were similar, while the microscopic were slightly variable. Significant difference (p< 0.05) was found in proportion of rays and fiber. All fiber dimensions were significant (p< 0.05), except for fiber length. Acacia hybrid showed a specific microscopic feature compared to their pure parent species. The results suggest that the change in genetic behavior through breeding process seemed potentially affected the change in wood anatomical structure of the four Acacias.