Objective: To identify the prevalence of soil-transmitted helminthiasis (STH) among school-age children in the Cagayan Valley, the Philippines, assess their level of awareness on the disease, and determine predisposing factors of the disease. Methods: A total of 478 Grades III-V school-age children in Pamplona and Sanchez-Mira School Districts in the Cagayan Valley answered the questionnaire assessing their knowledge, attitude, and practices on STH, subjected to anthropometric measurements, and provided faecal samples for parasitologic assessment (direct smear, Kato-Katz, and formol-ether concentration techniques). Results: The participants of the study, with 55.86% females, were 8 to 14 years old. Their nutritional status was assessed 'normal' (84.31%), 'severely wasted' (6.49%), 'wasted' (5.23%), 'overweight' (2.72%), and 'obese' (1.26%). The prevalence of infection with at least 1 STH species was 25.99% in Pamplona and 19.40% in Sanchez- Mira. Overall, the prevalence of heavy intensity was 7.11% for Ascaris lumbricoides and 1.67% for Trichuris trichiura. All hookworm infections had light intensities. The majority of the school-age children had a low score in the KAP test. In knowledge of STH, 'stunted growth as a symptom of infection' was associated with a lower risk of Ascaris lumbricoides infection (OR 0.448; 95% CI 0.212, 0.945; P=0.035) while 'playing with soil as a mode of transmission' was associated with an increased risk of Ascaris lumbricoides infection (OR 2.067; 95% CI 1.014, 4.212; P=0.046). In attitude towards STH, 'I think I have intestinal worm now' was associated with a higher risk of Ascaris lumbricoides infection (OR 1.681; 95% CI 1.061, 2.662; P=0.027). Conclusions: The prevalence rate of Ascaris lumbricoides among the school-age children in the Cagayan Valley shows the need to further intensify intervention in the area to meet the threshold set by the World Health Organization. The identified predictors of infection, which concerns the school-age children's knowledge and attitude toward STH, can be used in augmenting intervention programs in the future.