| Cassia orcuttii (Britton & Rose) B.L. Turner, 1949 |
| Cassia ovalifolia M. Martens & Galeotti, 1843 |
| Cassia oxyphylla Kunth, 1823 |
| Cassia pallida Vahl, 1807 |
| Cassia pallidior Rose, 1927 |
| Cassia palmeri S. Watson, 1887 |
| Cassia papillosa (Britton & Rose) Standl., 1933 |
| Cassia parahyba Vell., 1825 |
| Cassia parralensis H.S. Irwin & Barneby, 1975 |
| Cassia patellaria DC. ex Collad., 1816 |
| Cassia patellaria var. glabrata Vogel, 1837 |
| Cassia patellaria var. ramosa Vogel, 1837 |
| Cassia pavoniana G. Don, 1832 |
| Cassia pendula Humb. & Bonpl. ex Willd., 1809 |
| Cassia pentagonia Mill., 1768 |
| Cassia peralteana Kunth, 1824 |
| Cassia petensis (Britton & Rose) Standl., 1935 |
| Cassia picachensis Brandegee, 1915 |
| Cassia pilifera Benth., 1871 |
| Cassia pilifera var. subglabra S. Moore, 1895 |