| Ageratina calophylla (Greene) R.M. King & H. Rob., 1970 |
| Ageratina campyloclada (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina capillipes R.M. King & H. Rob., 1990 |
| Ageratina cardiophylla (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina carmonis (Standl. & Steyerm.) R.M. King & H. Rob., 1981 |
| Ageratina cerifera (McVaugh) R.M. King & H. Rob., 1972 |
| Ageratina chapalensis (S. Watson) R.M. King & H. Rob., 1970 |
| Ageratina chazaroana B.L. Turner, 1989 |
| Ageratina chiapensis (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina chimalapana B.L. Turner, 1989 |
| Ageratina choricephala (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina ciliata (Less.) R.M. King & H. Rob., 1970 |
| Ageratina colimana B.L. Turner, 2008 |
| Ageratina collodes (B.L. Rob. & Greenm.) R.M. King & H. Rob., 1970 |
| Ageratina concordiana B.L. Turner, 2012 |
| Ageratina conspicua (Kunth & Bouché) R.M. King & H. Rob., 1970 |
| Ageratina crassimonticola Rzed., 2018 |
| Ageratina crassiramea (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina cremasta (B.L. Rob.) R.M. King & H. Rob., 1970 |
| Ageratina crenaea (B.L. Rob.) R.M. King & H. Rob., 1970 |