We aimed to assess the risk factors for left ventricle (LV) enlargement in children with idiopathic frequent ventricular premature complexes (VPC) and discuss the clinical features and treatment strategies. Children diagnosed with idiopathic frequent VPC at Xinhua Hospital affiliated to the Shanghai Jiao Tong University during 2013 to 2019 were retrospectively evaluated. Gender, age, body mass index, weight, number and sources of frequent VPC, and changes in the LV structure were analyzed and compared. A total of 29 patient showed changes in LV enlargement at diagnosis [age 7.3 ± 4.0 years, 8 (24.1%) had symptoms such as syncope, palpitations, fatigue, and dizziness], whereas 220 showed a normal LV structure [age 7.2 ± 4.5 years, 77 (32.3%) with symptoms]. Patients with LV enlargement showed a higher percentage of VPC on Holter recordings (30.2 ± 10.7 versus 9.4 ± 6.9, p < 0.05), higher prevalence of ventricular tachycardia [22 (75.9%) vs 36 (16.4%), p < 0.0001], higher number of couplets [26 (96.7%) vs 132 (60.0%), p = 0.002], higher number of trigeminy [27 (97.8%) vs 133 (83.2%), p < 0.001], higher QRS wave width [80.0 ± 5.9 vs 77.8 ± 6.8, p = 0.021], and higher incidence of right bundle branch block [11 (37.9%) vs 2 (0.9%), p < 0.001]. Multivariate analysis suggested that right bundle branch block (Odds Ratio = 143.9 p <0.001) and VPC burden (>20%) (Odds Ratio = 132.6, p <0.001) were the risk factors for LV enlargement in children with idiopathic frequent VPC. In conclusion, frequent VPC can induce prominent enlargement or LV dysfunction in children. LV enlargement are reversible after catheter ablation or medication.