An increasing number of young children play video games at a very early age. Whereas studies have documented the negative effects of video gaming by young children, recent evidence suggests that playing video games may facilitate peer interaction and foster prosocial behavior. However, no systematic investigation has been made to examine the potential effects of video games on young children’s social development. The aim of this study is to exam whether brief exposure to two-player cooperative/competitive video games may promote young children’s peer communication and prosocial behavior. Sixty 4- to 6-year old children (34 boys) participated in this study. They were divided into two age groups: 30 younger preschoolers (Mage = 5.18, SD = .26) and 30 older kindergarteners (Mage = 6.04, SD = .29). Based on participants’ nominations of all their friends, the children were grouped into 30 pairs matched by gender and no friendship relationship. Each pair of children was randomly assigned to play a two-player cooperative or competitive game. After rating the affection for their partners and playing the games for 5 minutes, the children answered a battery of questions, including: (1) how much they liked their partners then, (2) how much they would like to play video games again with their partner or another same-gendered non-friend partner, and (3) which tangram puzzle they would assign to their current partner or a different non-friend partner. One day after the experiment, the children nominated all their friends again. This same socio-metric measurement was repeated in another 80-day follow-up interview to explore the long-term effects of video games on peer relationships. We used a 2 (test time: pretest vs. posttest) × 2 (game type: cooperative vs. competitive) × 2 (age group: younger preschooler, older kindergartener) design to evaluate children’s affection for their partners. We also used a 2 (game type: cooperative, competitive) × 2 (age group: younger preschooler, older kindergarteners) × 2 (communication target: current partner vs. new partner) design to assess children’s prosocial behavior and their willingness to communicate and collaborate with their counterparts. We obtained the following results: (1) After co-playing two-player video games for 5 minutes, children liked their partners more than they did before the game, and they preferred their current partner over a new partner for future games. One day after the experiment, all children nominated their video game partner as their new friend even though the partner was not a friend prior to the game; the new friendship lasted more than 80 days. (2) Compared to those who played competitive games, children who played cooperative games liked their partner more dearly. For the competitive game players, winners liked their partner more than did losers. (3) Compared to younger preschoolers, older kindergarteners liked their partner more dearly and were more willing to play with the new partner. (4) Children exhibited more helping behavior towards their partner than they did towards the new non-friend partner. These findings imply that brief exposure to appropriate two-player video games, such as cooperative games, may serve to promote young children’s peer communication and prosocial behavior towards their partners.