Aims and objectives: This study examines the role of age of first exposure and experience with input in the syntax of English–Spanish bilinguals. More specifically, I examine the production of clitic climbing constructions in Spanish (e.g., lo quiero ver “[I] want to see it” [Kayne; Rizzi]). Design/methodology: I compare two experimental groups of heritage speakers of Spanish ( n = 16) and L2 Spanish learners ( n = 17) from the United States (matched in proficiency) against a group of native Spanish speakers from Mexico ( n = 20). A sentence completion task was employed to elicit proclitic sentences across four verbal conditions: two in which clitic climbing is possible but with a higher or lower probability of occurrence, and two in which proclitic placement is agrammatical. Data and analysis: Results show a strong tendency to avoid clitic climbing constructions across all testing conditions. Two logistic regression analyses report no differences across all groups, who only favored the proclisis in highly grammaticalized verbs; proficiency among the experimental groups was a predictor in the production of these sentences. Findings/conclusions: A different time of onset of first exposure to the second language and a different experience with linguistic input (heritage language acquisition vs L2 acquisition) do not appear to affect the production of complex proclitic sentences in Spanish. Originality: Previous studies have employed a few selected periphrastic conditions to elicit clitic climbing constructions among English–Spanish bilinguals. This study further expands the range of verbal matrices employed in the four testing conditions and uses a more controlled testing environment. Significance: This study adds adult bilingual data to the ongoing debate on whether an early exposure to the second language results in advantages in the morphosyntactic domain.