The vascular flora of the park consists of 313 taxa. In addition, 146 taxa have been described among bryophytes, fungi and lichens. About the marine flora, a total of 105 taxa have been identified.

The island has endemic species such as Aeonium lancerottense, Allium subhirsutum obtusitepalum, Echium lancerottense var. Lancerottense, Helichrysum monogynum and Policarpaea robust.

Of all the listed species for the national park, 22 are in some category of protection and 2 of them, Asparagus nesiotes purpuriensis and Aichryson tortuosum, are in the category of vulnerable, according to the Law of the Canary Island Catalogue of Protected Species.

The lichens crustaceans establish themselves in areas near the coast, creating a verrucous and granulated scab on the rock. In the badlands, dense populations of the lichen Sterocaulum vesubianum appear, giving a whitish appearance on the northern side of the lava flow. The highest volcanic buildings influenced by the trade winds show yellow-greenish shades, with populations of different species of the genus Ramalina, with a predominance of R. bourgaeana.

In places that were not covered by the lava flows, another type of vegetation develops. It is of larger scale and presents structures adapted to adverse conditions, leaves transformed in thorns, superficial roots or stems and succulent leaves. Thus, in El Mojón, Halcones, Juan Perdomo or la Montaña Termesana, the most abundant species are the tabaiba dulce ( Euphorbia balsamifera) and the berode (Kleinia neriifolia), accompanied by the espino de mar (Lycium intricatum), the sogal ( Salsola vermiculata) and the algauera (Chenoleoides tomentosa).

In degraded areas, the ahulaga (Launaea arborescens) highlights, with great colonizing capacity and used for geothermal demos in the islet of Hilario. Together with it, the barrilla (Mesembryanthemum crystallinum), the cenizo (Chenopodium murale ) and the malva ( Malva parviflora ) form small pastures in soils that are rich in nitrogen.

The lapillus, which covers large areas in the national park, presents certain characteristics that favour the colonization of plants, showing a high capacity to reduce evaporation, to prevent the run-off and to maintain the humidity. These areas were colonized by species such as the malvarrosa (Pelargonium capitatum), the vinagrera (Rumex lunaria ) or the junco (Juncus acutus), which, in areas where the edaphic humidity is high, is arranged in linear formations, as in the slopes of the Macizo del Fuego.

In the coastal belt of halophiles (nearly 8 kilometres), subjected to a strong influence of the sea breeze, there are species able to withstand and even to take advantage of the water of the sea winds, in spite of its high salt content. Among the most representative and abundant species of this coastal thicket, the uva del mar (Zygophyllum fontanesii) highlights. In some places, such as El Mojón, it is accompanied by the tomillo marino (Frankenia capitata).

The coastal rocky bottom of the national park is upholstered by algae, which constitute an important source of nutrition for many marine species.