Handshape works differently in nouns versus a class of verbs in American Sign Language (ASL) and thus can serve as a cue to distinguish between these two word classes. Handshapes representing characteristics of the object itself ("object" handshapes) and handshapes representing how the object is handled ("handling" handshapes) appear in both nouns and a particular type of verb, classifier predicates, in ASL. When used as nouns, "object" and "handling" handshapes are phonemic--that is, they are specified in dictionary entries and do not vary with grammatical context. In contrast, when used as classifier predicates, "object" and "handling" handshapes do vary with grammatical context for both morphological and syntactic reasons. We ask here when young deaf children learning ASL acquire the word class distinction signaled by handshape. Specifically, we determined the age at which children systematically vary "object" versus "handling" handshapes as a function of grammatical context in classifier predicates but not in the nouns that accompany those predicates. We asked 4-6-year-old children, 7-10-year-old children, and adults, all of whom were native ASL signers, to describe a series of vignettes designed to elicit "object" and "handling" handshapes in both nouns and classifier predicates. We found that all of the children behaved like adults with respect to all nouns, systematically varying "object" and "handling" handshapes as a function of type of item and "not" grammatical context. The children also behaved like adults with respect to certain classifiers, systematically varying handshape type as a function of grammatical context for items whose nouns have "handling" handshapes. The children differed from adults in that they did not systematically vary handshape as a function of grammatical context for items whose nouns have "object" handshapes. These findings extend previous work by showing that children require developmental time to acquire the full morphological system underlying classifier predicates in sign language, just as children acquiring complex morphology in spoken languages do. In addition, we show for the first time that children acquiring ASL treat "object" and "handling" handshapes differently as a function of their status as nouns vs. classifier predicates, and thus display a distinction between these word classes as early as 4 years of age. (Contains 8 footnotes, 1 table, and 5 figures.)