Based on the tenets of Vygotsky’s sociocultural theory, this research study investigated the private speech produced by 30 adult English/Spanish bilinguals while engaged in a problem-solving activity, with the objective of better understanding the regulatory role that each language plays in the bilingual mind. In order to obtain a spontaneous production of private speech, participants were unknowingly audio-recorded while working in a private room on 15 challenging questions in Spanish, which included problems of logic, mathematics, visual-spatial problems, and kinship questions. The 30 early bilinguals who participated were divided into three groups: The Spanish-dominant group, the English-dominant group, and the balanced group, who consisted of bilinguals who reported to be equally comfortable in both languages. Results showed that bilinguals’ dominant language played an important regulatory role in their verbalized thinking while the other language provided a complementary set of cognitive resources and strategies that were employed when needed.