Four experiments explored the age of acquisition effects in the first and second languages of dominant Spanish-English bilinguals. In Experiment 1 (picture naming task) and Experiment 2 (lexical decision task), an age of acquisition effect was observed in a second language acquired after childhood as well as in the first language. The results suggest that age of acquisition effects reflect the order of word acquisition, which may in turn reflect the state of the lexical network when new words are learnt. The results do not support the idea that age of acquisition effects reflect differences between words learned during some critical period in childhood and words learned later in life. In Experiments 3 and 4, the age/order of second language acquisition affected lexical decision latencies regardless of the age at which translation equivalents were acquired in the first language, suggesting that the age of acquisition effect is linked to the acquisition of word forms rather than meanings.