There have been many studies exploring the advantages that bilingualism confers to individuals' working memory and metacognition (see Ransdell, 2006; Del Missier et al., 2010). The hypothesis of language critical period states that if no language learning and teaching happen during the critical period, an individual will never be able to fully grasp any language to a full extent (Fromkin et al., 1974). This study investigates whether late bilingualism (second language acquisition after the critical period) will positively affect a person's working memory and metacognition just like early bilingualism (second language acquisition before the critical period) does. Sixty Chinese persons between the ages of 18 and 35 participated in my online experimental protocol, including a language experience questionnaire, a reading comprehension exam, and a reading span task. I found that late bilingualism poses a similar advantage to an individual's working memory as early bilingualism, while it negatively affects an individual's metacognitive awareness of their own language ability.