The number of students pursuing Science, Technology, Engineering, and Mathematics (STEM) subjects and careers is a growing concern, with significant implications for societal progress and global challenges. There is currently a strong STEM policy drive to promote the uptake of STEM subjects. Evidence suggests that interest in STEM subjects and career choices begin to form at primary school age. However, there has been no research on upper Irish primary school children’s attitudes towards STEM and/or their interest in STEM careers. This study presents baseline data on children's STEM attitudes, conceptualised as self-efficacy and expectancy-value beliefs, collected using the upper primary school S-STEM Survey. A total of 373 upper-primary school children (aged 9 years – 13 years) in Ireland completed the survey. Findings indicate children have a positive attitude towards STEM and STEM subjects except for science, which received neutral responses. Gender differences were observed, with boys showing more positive attitudes towards mathematics, engineering and technology and STEM overall, compared to girls. A strong positive correlation between attitudes towards STEM subjects and interest in associated STEM careers was reported. These findings underscore the need for targeted STEM policy initiatives and purposeful intervention at primary school level to foster positive attitudes and interest in STEM careers.