The popularity of watching movies and videos on handheld devices is rising, yet little attention has been paid to its impact on viewer behaviour. Smartphone spectatorship is characterized by the small handheld screen as well as the viewing environment where various unrelated stimuli can occur, providing possible distractions from viewing. Previous research suggests that screen size, handheld control, and external stimuli can affect viewing experience; however, no prior studies have combined these factors or applied them for the specific case of smartphones. In the present study, we compared smartphone and large-screen viewing of feature films in the presence and absence of external distractors. Using a combination of eye tracking, electrodermal activity measures, self-reports, and recollection accuracy tests, we measured smartphone-accustomed viewers’ attention, arousal, engagement, and comprehension. The results revealed the impact of viewing conditions on eye movements, gaze dispersion, electrodermal activity, self-reports of engagement, as well as comprehension. These findings show that smartphone viewing is more effective when there are no distractions, and smartphone viewers are more likely to be affected by external stimuli. In addition, watching large stationary screens in designated viewing environments increases engagement with a movie.