Abstarct: The significance of problem-solving tasks in the realm of vocabulary learning is paramount, offering a dynamic approach to language acquisition by embedding linguistic knowledge within meaningful contextual challenges. This study aimed to investigate the effect of problem-solving tasks on both incidental and intentional vocabulary learning among elementary-level English language learners. The participants, comprising 40 students aged 18 to 21, engaged in distinct problem-solving tasks, with two intact experimental groups focusing on incidental and intentional vocabulary learning, respectively. The study employed proficiency tests, vocabulary pre-tests, and post-tests as instruments to measure vocabulary acquisition. Statistical analyses, including paired-sample t-tests and independent sample t-tests, were conducted to evaluate the effectiveness of problem-solving tasks in enhancing vocabulary learning outcomes. The findings revealed significant improvements in both incidental and intentional vocabulary learning, supported by substantial mean differences and large effect sizes. Additionally, the incidental group indicated a more considerable enhancement. The implications of these results extended to teachers, learners, and material developers, advocating for the integration of diverse problem-solving tasks into language learning curricula to foster robust vocabulary acquisition.