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E. furtivus is a medium-sized moth (approx 3.2-3.5 cm wingspan), similar to E. idahoensis but with lighter brown forewings and with a contrasting pale cubital vein. The costa and the orbicular spot are very light grey, but the reniform is infused with darker grey scales closer to the ground color. There is a black basal streak, and the discal area before the orbicular and between the orbicular and reniform is black. The lower half of the forewing is light brown, usually with a buff or slightly rust tone. The terminal area is dark brown, and is divided by a thin pale subterminal line. Several dark saggitate spots cross the paler subterminal area to the postmedian line. The overall appearance is much paler and streakier than that of idahoensis. The hindwings are light smoky brown with a faint discal mark, and the veins are lightly marked with darker scales. Sexes similar. The paler color and lighter cubital vein will separate most specimens of furtivus from idahoensis and the two similar and closely related but as yet (2002) undescribed species. See also E. clausa, which is slightly paler and has longer antennal pectinations. Euxoa furtivus belongs to the detersa group of the subgenus Euxoa. Until very recently (2000), it has been treated as a pale form of idahoensis. The specimens numbered 7 and 8 and identified as idahoensis in Lafontaine 1981, as well as two of the specimens illustrated as idahoensis in Lafontaine, 1987 (Plate 6, #37 and #38) are specimens of furtivus.

Euxoa furtivus has been collected from central Saskatchewan, west across southern Alberta to southern British Columbia, south to California and north to the Northwest Territories. The exact extent of its range is difficult to determine as it has only recently been re-elevated as a species separate from a complex of other species (the idahoensis group). In Alberta it has been collected mainly in the grasslands and southern montane regions, north to Nordegg.

Furtivus was originally described as a species of Agrotis from California. However, until very recently it has been treated as a pale form of idahoensis (Lafontaine, 1981; 1987). The specimens numbered 7 and 8 and identified as idahoensis in Lafontaine 1981, as well as two of the specimens illustrated as idahoensis in Lafontaine, 1987 (Plate 6, #37 and #38) are specimens of furtivus.