This study investigates the relationship among working memory (WM), first language (L1), second language (L2), and mathematics; with an aim to understand whether achievement in mathematics and L1 is related to performance in later L2 learning; and if so, whether WM components (i.e. phonological loop and central executive) play a role in this relationship between mathematics and language. A second objective of this study was to devise a computerized Turkish Reading Span Task.The participants were 60 university students. The data were collected quantitatively through 4 measures. To measure WM components, a computerized Turkish Reading Span Task and a Digit Span Task; to measure achievement in mathematics and L1, Transition to Higher Education Examination scores; and to measure achievement in L2, the preparatory school exam scores were used. Correlation analyses were performed via SPSS Version 18.The data analysis revealed (1) a relation of mathematical achievement to performance in L2 learning; and (2) a relation of achievement in L1 to performance in L2 learning. The findings indicate that achievement in mathematics and L1 is related to performance in later L2 learning, and WM is a significant factor in terms of the relationship between language and mathematics. In particular, the specific functions of the phonological loop are of pivotal importance for L2 and mathematics - but not for L1; whereas the specific functions of the central executive play more crucial role in L1 and L2 - but not in mathematics.