The study accessed the threat level of Mimosa pigra, Eupatorium odoratum and Eichhornia crassipes to flora in Tram Chim National Park by using the tour survey and standard quadrat setting method. Regarding canal and swamp habitats, Eichhornia crassipes had a very high threat level (IVI = 155.80% and the level 4 of association), reaching highest point in the rainy season. As regards the inside-dike habitats, Mimosa pigra had a high threat level (IVI = 70.79% and the level 4 of association), reaching the highest point in the dry season. Eupatorium odoratum had a moderate threat level (IVI = 49.99% and the level 3 of association). National Park’ managers enacted some effective controlling and management for Mimosa pigra and Eichhornia crassipes, but not for Eupatorium odoratum due to its low level of encroachment in the wild.