This study examined the second language (L2) speech development of a group of Chinese English as a Foreign Language (EFL) college-level learners (N = 83) and the association between their aptitude, anxiety, and L2 speech development. The performance of the participants' L2 speech, including speech comprehensibility and accentedness, was evaluated using a sentence reading task and a pair of picture description tasks (pre- and post-test). In addition, students completed the LLAMA tests (language learning and aptitude measurement in adults) and the Second Language Speaking Anxiety Scale (SLSAS). The t-test revealed that after one semester of English speaking and pronunciation instruction, the EFL students in the study demonstrated significant gains in their L2 speech performance in terms of accentedness and comprehensibility in both controlled and impromptu tasks. Regression analyses revealed that phonemic coding ability positively predicted gains in comprehensibility but negatively predicted gains in accentedness during sentence reading. In addition, associative memory was positively associated with comprehensibility gains in the picture description task. Anxiety appeared to be a strong predictor of participants' gains in speech comprehensibility and accentedness during the picture description task.