This study investigated whether the ability to learn word-object associations following minimal exposure (i.e., fast mapping) was associated with concurrent and later language abilities in children with ASD. Children who were poor learners at age 3½ had significantly lower receptive language abilities than children who successfully learned the new words, both concurrently (n = 59) and 2 years later (n = 53), lending ecological validity to experimental fast-mapping tasks. Fast mapping comprehension at age 3½ was associated with better language outcomes regardless of whether children had produced the new words. These findings highlight the importance of investigating processes of language learning in children with ASD. Understanding these processes will enable the development of maximally effective strategies for supporting word learning.