Relative to the tendency to empathize with and help sociocultural in-group members, there are often social and psychological barriers to responding prosocially toward out-group members. This experiment examined the roles of mindfulness instruction and compassion instruction in fostering prosocial behavior toward an ethnic out-group (non-U.S. Arabs) relative to an ethnic in-group (U.S. residents). The study also examined whether contemplative practices would predict less parochial empathy and whether parochial empathy would mediate the relations between mindfulness/compassion and prosocial behavior toward the out-group. A national sample of n = 450 U.S. residents was recruited online via the Prolific platform using the standard sample function, which distributed the study to available participants on Prolific. Participants were randomly assigned to one of three brief, structurally equivalent audio-recorded instruction conditions: mindfulness meditation, compassion meditation, or a relaxation control, and then completed a series of tasks to assess prosociality toward in- and out-group members. The compassion training was most effective in reducing parochial empathy when controlling for all covariates. The mindfulness training reduced parochial empathy when controlling for in-group empathy, and it led to greater out-group altruism and support for out-group immigration. Parochial empathy predicted out-group altruism; however, it was not a better predictor of support for Arab immigration than trait empathic concern. Training conditions did not differ on support for out-group cause. Exploratory moderation analyses found that those with higher trait empathic concern and intergroup contact quality were more likely to show compassion training and mindfulness training effects, respectively, on support for out-group immigration. Brief compassion training had the strongest effect on parochial empathy, but mindfulness training showed stronger effects on out-group altruism and support for out-group immigration. Predisposing social psychological characteristics may enhance intergroup prosociality among those receiving compassion or mindfulness instruction. This study is preregistered at https://osf.io/rnc97. The online version contains supplementary material available at 10.1007/s12671-023-02100-z.