Background: An excess risk of leukemia in children living close to high-voltage power-lines and therefore exposed to extremely low frequency magnetic fields has been suggested, though not all studies yielded consistent results, and a possible role of confounding and exposure misclassification could not be entirely ruled out. Methods: We investigated the risk of childhood leukemia associated with magnetic fields exposure from 132+ kV power lines within a population-based case-control study in two Northern Italy provinces, Modena and Reggio Emilia. We included all the 182 registry-based childhood leukemia cases diagnosed from 1998 to 2019, and 726 age, sex and province of residence-matched controls. We assessed exposure by calculating distance from house to nearest power line in a geographical information system database and by modeling magnetic fields at the subjects’ residence. We run analyses in the overall population, restricted to acute lymphoblastic leukemia (ALL) cases, and stratified by age (<5 and ≥5 years). Results: Compared to those living ≥ 400 m from high-voltage power-lines, children living <50 m and 50-<100 m from power lines showed a disease odds ratio (OR) of 3.0 (95% CI 0.7-13.3) and 1.6 (95% CI 0.5-5.1), respectively. The excess risk close to the power lines was higher for the ALL subtype (OR 3.0, 95% CI 0.7-13.3) and among children diagnosed after 5 years (4.1, 95% CI 0.8-20.6). Results did not substantially differ when exposure was based on modeled magnetic fields, though risk ratio estimates became more statistically unstable. Conclusions: We found a statistically imprecise excess risk for childhood leukemia associated with close proximity to high-voltage power lines, which appeared to be stronger for the youngest children.