The main aim of the present study was to examine state levels of loneliness in adolescence. Both concurrent associations and temporal dynamics between social contexts and state levels of loneliness were examined. Data were collected from 286 adolescents (M[subscript age] = 14.19 years, 59% girls) by using the Experience Sampling Method. Results showed that adolescents had higher levels of state loneliness when they were alone, compared with being with company. When adolescents were with others, they were most lonely at school and with classmates. Adolescents showed a relief effect when they entered the company of friends after being alone, whereas a spillover effect of solitude was found when adolescents entered the company of family after being alone. Our findings show the dynamics of state loneliness, in that being with classmates increases state loneliness, whereas being with friends reduces loneliness after being alone.