The present study examined the impact of implicit mood manipulation on the scope of visual processing. Previous studies have shown that the scope expands when participants explicitly receive positive mood manipulation. Thus it is unclear whether the same principle applies to the case in which participants’ mood is induced implicitly. We adopted an implicit mood manipulation in which participants held a pen in their teeth so that the muscles associated with smiling are activated without explicitly requiring to pose in a smiling face (Strack, Martin, & Stepper, 1988). Under the control condition, participants held the pen with lips to inhibit those muscles. Before and after the pen-holding, participants viewed bi-stable figures (e.g., Rubin Vase) and reported the timings which their percept (narrow or broad perspective) flipped. The result indicated successful mood induction: the teeth group rated comic-stimuli funnier than the control group. None of the participants were unaware of the purpose of the manipulation. Most importantly, the dominance of the broad percepts of the bi-stable figures was greater under the teeth condition. No such effect was found under the lip condition. These results suggest that the positive mood with implicit peripheral facial-muscle control broadens the scope of visual processing.