| Acacia sinaloensis Saff., 1914 |
| Acacia smallii Isely, 1969 |
| Acacia sonorensis Rose, 1903 |
| Acacia sororia Standl., 1919 |
| Acacia sousae L. Rico, 1987 |
| Acacia sphaerocephala Schltdl. & Cham., 1830 |
| Acacia standleyi Saff., 1914 |
| Acacia stipellata Schltdl., 1838 |
| Acacia subangulata Rose, 1899 |
| Acacia subtortuosa Shafer, 1908 |
| Acacia suffrutescens Rose, 1909 |
| Acacia tenuifolia (L.) Willd., 1806 |
| Acacia tenuifolia var. tenuifolia (L.) Willd., 1806 |
| Acacia tepicana Saff., 1914 |
| Acacia tequilana S. Watson, 1890 |
| Acacia tetragona Willd., 1806 |
| Acacia texensis Torr. & A. Gray, 1840 |
| Acacia tortuosa (L.) Willd., 1806 |
| Acacia tortuosa Billb. ex Beurl., 1856 |
| Acacia trichandra Zucc., 1837 |