This study documented how children's decisions to trust and help partners in a game depend on the game's incentives. Adults, 5-, 7-, and 9-year-olds (N=128) guessed the location of hidden prizes, assisted by a partner who observed the hiding. After each hiding event the partner shared information with participants about the prize's location. Participants earned prizes every time they guessed correctly. The partner earned prizes either from participants' correct (cooperation incentive) or incorrect (competition incentive) guesses. Children and adults trusted their partner more often when the game incentivized cooperation versus competition. A complementary pattern was observed when participants assisted their partner find prizes they observed being hidden: Participants strategically shared truthful information more often when the game rewarded cooperation.