Word-learning development is extremely varied among children with autism, with some showing a peak of abilities in vocabulary and others little or no comprehension or expression of isolated words. Typical word learning mechanisms, such as the application of mutual exclusivity, cross-situational mapping, the whole-object principle, and the noun-naming bias also share this heterogeneity: some mechanisms appear to develop in a typical fashion and others depend on the individuals’ language level. The reason for which word-learning processes could be atypical in autism is still the object of debate. Atypical attentional biases or early social interaction could both play a role in early word acquisition. But it is also unclear whether differences in vocabulary acquisition simply reflect the impact of co-morbid language impairment or there is a degree of specificity in autism. Finally, I propose that a more dimensional view in the study of word learning could be useful to move the field forward.