Cooperation is a universal phenomenon involving individuals working together to achieve a shared goal. Little attention has been given to how harsh environments in terms of childhood adversities and family unpredictability might be linked to individual's engagement in cooperative behaviors and on how the persons' physiological ability to adapt to the environment might influence this association. To fill this gap, we conducted two studies. The first showed in 1296 participants (44.44 % male, Mage = 29.95, SD = 11.50) that adversities favor cooperation as individuals may strengthen bonds to alleviate the threats of environmental adversities, whereas family unpredictability hinders individuals' willingness to cooperate as opting for certain non-cooperative gains when they are available is preferred over taking risks with uncertain cooperative outcomes. The second showed in 88 undergraduate students (47.72 % male, Mage = 23.67, SD = 4.91) showed the moderating role of individuals' physiological self-regulation as indexed by cardiac vagal tone (CVT) in the previously found environment-cooperation link. Specifically, higher CVT promotes more consistent cooperative behaviors when facing higher levels of adversities, and lower CVT exacerbates the impact of both childhood adversities and family unpredictability reducing the probability of engaging in cooperative behaviors. Given the protective role of physiological regulation, when facing harsh childhood environments, interventions that strengthen this factor should be investigated in relation to prosocial behavior.