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A medium-size (approx 2.5 cm wingspan) broad-winged brownish-grey geometrid moth. The forewings are crossed by an incomplete antemedian and complete and prominent postmedian line, buff-yellow in color and, the latter also reappearing across the lower half of the hindwings. There is a well-developed discal spot on each forewing, and a less distinct one on the hindwings. In males in particular there is usually a series of poorly defined dark spots or blotches marking the median line and crossing the forewings distad to the postmedian line. The veins on the outer half of the forewings are finely lined by pale yellow scales. The pale yellow postmedian lines across both wings lacking a border of dark scales can be used to separate irrorata from other Alberta Digrammia species (i.e. D. mellistrigata).