Probably polylectic although its true status is unknown. Pollen sources on the continent are not known.
As a result of studies made in 2010 the sole known pollen resource in Britain is apparently L. corniculatus (Fabaceae). The species is tentatively regarded on available evidence as being at least narrowly oligolectic on Fabaceae. Female Lasioglossum angusticeps may of course visit flowers of other species of Fabaceae but this has not been confirmed. Analysis of the pollen on a female bee collected by M. Edwards at Chideock, Dorset had two pollen grains of a Trifolium in amongst thousands of Lotus.
G.R. Else considers females of this species to be inseparable from those of Lasioglossum punctatissimum (which sometimes shares the same habitat as L. angusticeps) and it is thus not possible to confirm flower records for this sex. However, females considered to be this species, have been noted flying in numbers to Lotus corniculatus (Fabaceae) in Dorset and the Isle of Wight (pers.obs.). Males have been collected from yellow-flowered Asteraceae and Daucus carota (Apiaceae)
Ebmer (1971) lists Stachys (Lamiaceae) as a forage plant.