There has been increased interest in the relationships between religiosity, meditation practice and well-being, but there is lack of understanding as to how specific religious components and distinct meditation practices could influence different positive and negative psychological adjustment outcomes. The aim of this study was to assess the explanatory power of religious beliefs and the practice of prayer, focused attention (FA), open monitoring (OM), and compassion meditation (CM) on psychological adjustment, taking into consideration a number of practice-related variables such as session length, frequency of practice and lifetime practice. Psychological adjustment was assessed by means of happiness, positive affect, depression, negative affect, and emotional overproduction. A cross-sectional design was used, with a final sample comprising 210 Spanish participants who completed an online assessment protocol. Hierarchical regressions were performed, including age, sex and psychotropic medication use in the first step as possible confounders, with the addition of religious beliefs and the practice of prayer, FA, OM, and CM in the second step. FA session length was related to all psychological adjustment outcomes: happiness (ΔR 2 = 0.09, p = 0.002; β = 0.25, p = 0.001), positive affect (ΔR 2 = 0.09, p = 0.002; β = 0.18, p = 0.014), depression (ΔR2 = 0.07, p = 0.004; β = -0.27, p < 0.001), negative affect (ΔR 2 = 0.08, p = 0.007; β = -0.27, p < 0.001) and emotional overproduction (ΔR 2 = 0.07, p = 0.013; β = -0.23, p = 0.001). CM session length was related to positive affect (β = 0.18, p = 0.011). CM practice frequency was associated with happiness (ΔR 2 = 0.06, p = 0.038; β = 0.16, p = 0.041). Lifetime practice of FA was related to happiness (ΔR 2 = 0.08, p = 0.007; β = 0.21, p = 0.030) and OM to emotional overproduction (ΔR 2 = 0.08, p = 0.037; β = -0.19, p = 0.047). Religious beliefs and prayer seemed to be less relevant than meditation practices such as FA, OM, and CM in explaining psychological adjustment. The distinct meditation practices might be differentially related to distinct psychological adjustment outcomes through different practice-related variables. However, research into other forms of institutional religiosity integrating social aspects of religion is required.