The paper examined the effect of a STEAM-based mathematics teaching intervention on students’ numerical fluency and gender differences in secondary schools within Tubah Sub-Division, Mezam Division, North West Region of Cameroon. The study employed a quasi-experimental design, involving 43 students from CCAST Bambili as the experimental group and 34 students from Technical High School Ntigi as the control group. Both groups were pre-tested on a common Form Three mathematics topic in statistics, before the experimental group was exposed to a three-week STEM-oriented instructional treatment. Post-test scores were then collected from both groups. Data were analyzed using descriptive and inferential statistics, including mean comparisons, t-tests, and graphical representations. Findings revealed that the experimental group significantly outperformed the control group in the post-test means score with an independent sample t-test showing t(75) = 6.42, p<0.001, demonstrating that STEAM-integrated instruction improved students’ engagement with mathematical tasks. Additionally, gender-based analysis revealed that female students in the experimental group achieved higher mean scores than their male peers, with a significant difference observed (t(41) =2.11, p<0.05). Suggesting that inclusive and context-sensitive STEAM pedagogies foster female learners’ achievement in mathematics, thereby challenging traditional gender performance gaps. Relying on these findings, the study concluded that STEAM-based teaching interventions are effective in fostering numerical proficiency among arts-oriented students while also reducing gender disparities in mathematics achievement. It recommended that mathematics teachers should adopt STEAM-oriented approaches to enhance critical thinking and problem-solving, and that educational policymakers should integrate gender-responsive STEAM practices into the curriculum to promote equity and inclusiveness in secondary school mathematics education.