The main purpose of this study is to analyze the effects of using Pokémon GO for 10 weeks on the cognitive performance (memory, selective attention, concentration, and creative imagination) and emotional intelligence (well-being, self-control, emotionality, and sociability) of Taiwanese primary students in the fifth and sixth grade. A mixed experimental design was used, with a control group (CG; n = 62) that did not use Pokémon GO, and an experimental group (n = 61) that used Pokémon GO for 10 weeks. Confounders were age, sex, education level of the family, number of computers in the home, daily study time, and Internet access. The results showed that the players spent about 40 minutes/day on this game during this period. Boys played more and won more points in the game than girls. Compared against their peers, the players playing Pokémon GO showed a significant increase in their selective attention (p = 0.025), concentration levels (p = 0.004), creative imagination (p < 0.001), emotionality (p = 0.001), and sociability levels (p = 0.005) but not memory, well-being, or self-control (all p > 0.05). It is concluded that Pokémon GO, in a playful way, could positively affect their cognitive performance (selective attention, concentration levels, and creative imagination) and improve their social relationships. However, if future researchers would like to ascertain whether Pokémon GO is a useful viable cognitive and social approach or not, more randomized controlled trial studies will be needed to compare Pokémon GO with traditional teaching approaches and educational methods.