Children with developmental coordination disorder (DCD) are more likely to develop cardiovascular disease (CVD) risk factors such as obesity and reduced cardio-respiratory fitness. It has also been shown that adolescents with probable DCD (p-DCD) have elevated cardiac output (CO) and stroke volume (SV) compared to typically developing (TD) controls, which in turn may heighten their risk of developing elevated left ventricle mass (LVM) or left ventricular hypertrophy (LVH). The purpose of this study was to assess left ventricular structure and function longitudinally in adolescents with and without p-DCD. This three year study included 86 adolescents with significant motor impairment (33) and TD controls (53). Adolescents were 12 years old at the beginning of the study. The Movement ABC test (M-ABC-2) was used to classify children as p-DCD. Cardiac dimensions were measured using ultrasound echocardiography. Body mass, fat mass (FM) and body mass index (BMI) were significantly elevated in the p-DCD group in all three years. Peak aerobic fitness normalized to fat-free mass (peak VO[subscript 2FFM]) was significantly elevated in the TD controls in each year. Heart rate was also increased in the p-DCD group in years one and three. A repeated measures ANCOVA with time-varying covariates was performed for CO and LVM on p-DCD while controlling for peak VO[subscript 2] and FFM. CO and LVM were significantly elevated in the p-DCD which remained constant over time. FM completely mediated the association between p-DCD and CO in adolescents. For LVM, both FM and CO accounted for elevated LVM in adolescents with p-DCD. In conclusion, elevated FM in adolescents with p-DCD contributes to a higher CO and LVM over time compared to TD controls. If this persists throughout adolescents and into adulthood, these adolescents may be at risk of developing LVH. (Contains 4 tables.)