Background: The influence of race/ethnicity on the relationship between sedentary screen time and left ventricular mass has been recently suggested, but remains a subject of debate, and has never been explored in Africa. Purpose: To determine whether there is a racial/ethnic influence on the relationship between sedentary screen time and left ventricular mass in MAGhreb and Sub Saharan Africa Left-Ventricul ArGEometry Study (MAG-SALVAGES) participants. Methods: 100 blacks sub-Saharan African and 187 white Maghreb aged 18 - 55 years underwent an interview on their behavioral measures, physical activity and eating habits. Their left ventricular mass has also been measured by a resting transthoracic echography according to the American Society of Echography. Generalized linear models evaluated a test-for-trend across higher levels of sedentary screen time in progressive models with left ventricular measurements as dependent variables. The study population was stratified into quartiles of sedentary screen time (separately for whites and blacks) and examined the joint association of sedentary screen time and LVM within quartiles of physical activity. Results: Among White Maghreb, higher screen time was associated with smaller left ventricular mass (P < 0.001). This association persisted when adjusting for age, gender, heart rate, waist circumference, waist-to-hip ratio, systolic blood pressure QRS duration, TAPS and PAPS. Whereas, in blacks sub-Saharan African, the left ventricular mass was not associated with sedentary screen time. Conclusions: Sedentary screen time is associated with smaller left ventricular mass in White Maghreb, not in black sub-Saharan African. The lack of association in blacks supports a potential qualitative difference in the cardiovascular consequences of sedentary screen based behavior.