PURPOSE: This study sought to (1) evaluate the perceived effectiveness of an early childhood cancer warning signs and symptoms (EWSS) training intervention on health care worker (HCW) knowledge, attitudes, and clinical practice; (2) evaluate the ease of implementation of training received, including potential barriers and facilitators; and (3) provide insights into program improvements for future iterations of the intervention. METHOD: Using a qualitative descriptive study design, we conducted in-depth, semistructured interviews with 23 purposively sampled Ghanaian HCW recipients of the EWSS training intervention. We undertook iterative thematic analysis of data concurrently with interviews and used a modified version of the theoretical framework of acceptability to guide the evaluation of the training intervention. RESULTS: We identified six themes-affective attitude, burden, intervention coherence, perceived effectiveness, self-efficacy, and quality improvement-that structure participant perceptions of the effectiveness of the EWSS training. Participants generally had a positive attitude to the training intervention, found the content relatively easy to understand, and communicated the positive impacts of the training on their day-to-day practice. However, they also identified patient- and system-level challenges to the real-world implementation of intervention components, including patients' cultural and religious beliefs about illnesses, patients' financial constraints, and inadequately funded health systems. CONCLUSION: Our findings suggest that although an HCW-focused training intervention has the potential to improve timely diagnosis and referral for childhood cancers in Ghana and comparable health system contexts, complementary interventions to address patient- and system-level implementation challenges are required to translate improvements in HCW knowledge to sustained impact on health outcomes for children with cancer.