This article aims to contribute to the debate on a feature-geometric approach versus a binary feature approach to number with data from the Eastern Algonquian language, Mi'gmaq. In Mi'gmaq, animate intransitive verbs show a three-way number contrast with singular, dual and plural. Nonsingular endings appear in both dual and plural forms. The plural is derived from the dual by adding a pluralizing morpheme, -ulti. Thus, the plural is morphologically more complex than the dual. A complex plural form is unexpected under Harley & Ritter (2002)'s feature geometry as plural is formally represented as being less complex (i.e, less features) than the dual. In a binary feature system as argued for by Noyer (1992), Harbour (2006), and Nevins (2011), singular, dual, and plural number are represented as being equally complex. A binary feature system can thus capture a wide range of empirical number patterns, including the one seen in Mi'gmaq. By associating morphemes with the feature-values, I argue that a binary feature system can better derive number agreement in Mi'gmaq. I also extend the binary feature approach to derive agreement between nouns, which have a singular-plural distinction, and verbs with the three-way contrast. I conclude with some implications of this analysis for theories of markedness.