Past studies have shown the patterning of affective responses during a graded exercise test (GXT) in adult and male adolescent populations, but none have explored the patterns in adolescent girls or younger children. This study explored the patterning of affective responses during a GXT in adolescents and younger children. Forty-nine children (21 male and 28 female) aged between 8–14 years (10.8 ± 1.8 years) completed a GXT. Ventilatory threshold (VT) was identified. At the end of each incremental step, participants reported affective valence. Results revealed that affective valence assessed by the Feeling Scale (FS) significantly declined from the onset of exercise until the point of VT in the younger children, but remained relatively stable in the adolescents. Exercise above the VT brought about significant declines in affective valence regardless of age or sex, but the decrease was significantly greater in adolescents. Results suggest it may be preferable to prescribe lower exercise intensities (below VT) for children, compared with adolescents, to ensure a positive affective response.