It grows in wetland areas where it does not have to compete with taller plants due to grazing by animals, periodic flooding during the winter-spring seasons, or mowing.

It grows in Western Europe from the Iberian Peninsula to the British Isles and Denmark in the north, as well as Poland, Slovakia, Hungary, Croatia, and Montenegro in the east.

[6] As a naturalized species, it has been reported from the Czech Republic,[6] North America,[7] and even from the Swartland region in the Western Cape province of South Africa.

[8] Throughout its range, the species is rarely encountered,[9] influenced by both its specific ecological requirements and its poor ability to spread over long distances.

[10] In the southern part of its range, it grows in mountainous areas (e.g., in Spain[11] and Morocco, at altitudes above 2300 meters above sea level).

[16] One of the notches between the teeth, especially on the third pair of leaflets from the bottom, is distinctly deeper, which is a significant diagnostic feature distinguishing this species from terrestrial forms of fool's watercress.

[13] The flowers are small, with white (sometimes cream or pinkish)[13] corolla petals reaching about 0.5 mm in length, mostly with a pointed and inwardly bent tip.

[13] This species, in its terrestrial form, can coexist with creeping marshwort in meadows and can be almost indistinguishable to such an extent that genetic research is necessary to determine the taxonomic affiliation of the plants.

[24] Another similar species, Helosciadium inundatum [pl], lacks bracts altogether, and its leaflets have wedge-shaped bases, not rounded as in creeping marshworts.

[13] Among plants with a molecular cloning type, creeping marshwort is included in the Fragaria vesca group characterized by the predominance of spreading through stolons with relatively short individual ramet lifespans.

[9] A complicating factor for generative reproduction may be excessive turf density and the lack of initial microsites free from vegetation.

They can be carried by water over long distances (in lake basins or along streams), but they can also be moved on a smaller scale within grassland communities during periodic floods, for example, after heavy rains.

[9] Creeping marshwort populations exhibit large fluctuations in the number of individuals depending on prevailing water conditions or other interactions, such as grazing.

[18] It occurs along water edges, especially lakeshores, in communities of low vegetation flooded outside the growing season, and in gaps in reed beds.

[18] In places flooded in winter and spring, the bare soil surface is exposed after the water level drops, enabling the development of light-demanding creeping marshwort.

[10] A constant feature of habitats is the near-neutral soil pH[10] and high humidity[28][18] (although often with a significant drop in water level by the end of summer).

[12] Due to the pioneer character of the species, a constant feature of its occupied sites is the high frequency and intensity of interactions leading to the limited development of competitive vegetation.

[10] The habitat characteristics conditioning the development of creeping marshwort include low vegetation height (optimally not exceeding 20 cm) or at least the presence of gaps (e.g., in reed beds), lack of shading caused by trees and shrubs, and absence of competitive expansive species (strongly growing ones).

[28] The most common accompanying species of creeping marshwort (growing with them on over 50% of sites in northern Germany) include: creeping bentgrass (Agrostis stolonifera), creeping buttercup (Ranunculus repens), silverweed (Potentilla anserina), water mint (Mentha aquatica), jointleaf rush (Juncus articulatus), hairy sedge (Carex hirta), white clover (Trifolium repens), common marsh bedstraw (Galium palustre), and Kentucky bluegrass (Poa pratensis).

Alongside dominants in these communities, the most common species include: water mint (Mentha aquatica), common marsh bedstraw (Galium palustre), true forget-me-not (Myosotis scorpioides), great yellow-cress (Rorippa palustris), and marsh speedwell (Veronica scutellata).

[31] On the Iberian Peninsula, creeping marshwort grows on the banks of mountain streams accompanied by Glyceria declinata.

[16] Earlier, based solely on morphological observations, such a hybrid was also described (as Apium × riddelsdellii Druce), but the diagnosis from 1917 is considered doubtful[24] (at the site, a morphologically very similar intergeneric hybrid between Helosciadium nodiflorum and lesser water-parsnip (Berula erecta) – × Beruladium – was also observed contemporarily, in addition to similar parent taxa).

[21] The species was first scientifically described as Sium repens by Nikolaus Joseph von Jacquin in his work Flora Austriaca, published in 1775.

[12] The name Helosciadium is derived from the combination of the Greek words hélos and skiás, meaning "swamp" and "canopy" respectively, inspired by the habitat occupied by these plants and the type of inflorescence.

Outside the climatic optimum of the species, extensive areas will be found in southern Europe, but also in lowlands from France through Germany to Poland.

Favorable conditions for the species will arise in higher mountain areas (mainly the Alps and the Carpathians) and in areas under the influence of an oceanic climate in Northern Europe (the central part of Great Britain, the Jutland Peninsula, the central part of the Scandinavian Peninsula).

[30][10] Protective measures involving the collection of plants from nature, their multiplication, and reinforcement of threatened populations, as well as the restoration of vanished sites, have also been successfully carried out in Poland in Gniezno and in the Przemęt Landscape Park.

[46] Due to its prostrate growth habit and its ability to form dense mats in favorable conditions, the plant is used as ground cover in sunny areas along pond banks.

[10] In the case of cultivation aimed at increasing the species' resources in nature, especially for creating new replacement habitats, it is recommended to propagate plants from seeds obtained from different populations.

Since losses are usually expected in the first year of cultivation, to obtain a sustainable population, it is recommended to use as much plant material as possible when creating replacement habitats.