Adolescence is a transitional period between childhood and adulthood. Nowadays, adolescents in Lebanon are growing during a time of unprecedented health crises and political instability. This study aimed to determine the prevalence and correlates of malnutrition, dietary diversity in adolescents’ households, and adolescents’ self-reported food insecurity in Lebanon. A national representative sample of 450 parent–adolescent dyads (parents: mean age ± standard deviation (SD) = 46.0 ± 7.0, mothers: 59.0%; adolescents: mean age ± SD = 15.0 ± 3.0, girls: 54.6%) were interviewed. Anthropometric and blood hemoglobin measurements were performed for adolescents. The Food Consumption Score, the Arab Family Food Security Scale and the Adolescent-Level Food-Security Scale were used. The overall prevalence of adolescent stunting, thinness, overweight, obesity and anemia was 6.7%, 4.7%, 19.3%, 12.9% and 16.7%, respectively. Almost 40.4% and 68% of adolescent’s households consumed undiversified diets and were food insecure, respectively. Food insecurity (FI) affected 54.0% of adolescents. Adolescents attending schools (vs. university) were eight times more likely to be stunted (p = 0.04). Boys had a 4.3 times higher thinness risk (p = 0.005) compared to girls. Households reporting an income decline since the start of the Lebanese economic crisis were three times more likely to have a thin adolescent (p = 0.01). Parental overweight/obesity (p = 0.002) and lower education level (p = 0.04) nearly doubled the risk of adolescent overweight or obesity. At a time when escalating crises in Lebanon are shifting diets for the youngest generations, the development of adolescent-responsive nutritional policies becomes a must.