Digitaria ciliaris and D. horizontalis are among the most common and harmful weed species of crops in Senegal. Their identification by taxonomists and agronomists is not easy because of their close similarity. The objective of this study is to define their morphological differences and to provide a practical identification key. The results of the study show that Digitaria ciliaris and D. horizontalis are differentiated from three characters in the vegetative and reproductive systems. An illustrated table of these discriminating traits, serving as a key of practical determination, is proposed.