A serious barrier to our understanding of urban ecosystems is a lack of information on the ecology of soils organisms of green spaces within large cities. This study addresses this gap by providing baseline survey data on the biodiversity of soil macrofauna in urban parks and domestic gardens of London, UK. In April and June 2004, the soil macrofauna were handsorted from soil cores in eleven parks and gardens of various sizes in central London. Five taxa were identified to species (Lumbricidae, Isopoda, Diplopoda, Chilopoda and Formicidae). The biodiversity value of the two main habitats (horticultural borders and mown grass lawns) was assessed and the influence of a range of environmental factors on species density (number of species per unit area) examined. The species densities of the studied soil invertebrates in the urban gardens were comparable with those found in natural ecosystems, although plant borders contained significantly more species than lawns. Borders had higher levels of plant nutrients, higher floristic diversity and lower levels of micronutrients and heavy metals than lawns. Significant predictor variables of species densities in the plant borders were the percentage of leaf litter cover, sampling month and soil pH. Species densities in the lawns were significantly correlated with the distance of the samples from the edge of the lawn.