Previous studies have suggested that attachment priming plays an important role in fostering insecure people's explicit prosocial attitudes. However, whether it exerts the same effect on implicit prosocial attitudes remains unclear. Two studies were conducted to examine the impact of attachment priming and mental depletion on insecure participants' implicit altruistic attitudes. In Study 1, participants (N = 100) were primed under 3 conditions (secure priming, positive priming, and neutral priming) before completing an Implicit Association Test assessing altruism. Results indicated that security priming, rather than positive or neutral priming, increased attachment anxious participants' implicit altruistic tendency, and this effect was not significant in participants with high avoidance. In Study 2, participants (N = 124) were involved in a 2 (attach-
ment name priming, acquaintance priming) x 2 (high mental depletion, low mental depletion) experimental design. The results supported the finding of Study 1 and, more importantly, further revealed that avoidant participants under attachment priming exhibited an implicit altruistic tendency in a high mental load condition. These findings extended the research on attachment priming to the implicit level and have practical implications for avoidant people to improve implicit prosocial tendency.