Abstract Pupil dilation is widely used as an index of emotional arousal, yet pupil size is also strongly shaped by visual luminance and by attention to luminance-defined objects. This overlap creates a challenge for affective pupillometry in dynamic visual environments, where emotional sounds may occur while attention shifts between bright and dark stimuli. We tested whether subjective emotional arousal predicts pupil responses under such conditions. Twenty-two participants listened to affective environmental sounds while viewing two superimposed moving dot fields, one bright and one dark, moving in opposite directions. At sound onset, participants shifted attention from one dot field to the other and then rated each sound for arousal and valence. Pupil responses were analyzed in 100-ms time bins from 0 to 6 s after sound onset using linear mixed-effects models that included within-participant standardized arousal and valence ratings, block, and rating-by-block interactions. Trial-by-trial arousal positively predicted pupil responses from 0.65 to 5.95 s after sound onset after false discovery rate correction, whereas valence showed no reliable independent effect. The arousal effect remained positive in robustness analyses controlling for baseline pupil size, eye-movement covariates, and within-block trial order. These findings show that subjective emotional arousal remains detectable in pupil dynamics even when attended luminance is changing. Affective pupillometry can therefore index trial-by-trial arousal in dynamic visual contexts, but its interpretation requires explicit consideration of visual-attentional influences on the pupil.