Research on the impacts of mindfulness trainings (MTs) on teachers' psychological health and wellbeing suggests that MTs may be especially well-suited to preparing teachers for the unique demands of the profession (Iancu et al., 2017; Klingbeil & Renshaw, 2018). However, few studies have investigated whether different teachers benefit in different ways from mindfulness training, although there is some evidence that mindfulness training may yield dissociable benefits (Fucci et al., 2018; Hildebrandt, McCall, & Singer, 2017; Sauer-Zavala, Walsh, Eisenlohr-Moul, & Lykins, 2013) and preliminary evidence of differential effects of MTs on subgroup of teachers (Abenavoli et al., 2013; Roeser et al., 2021). The paucity of empirical evidence may be partly attributed to the paucity of theoretical frameworks that identify possible mechanisms for differential effects (Sedlmeier et al., 2012). The present study stepped into this gap by synthesizing the contemplative science literature with historical and contemporary theories of motivation and coping to propose a new theoretical framework for differential effects that highlighted motivation as a potential predictor of subgroup differences. This framework included a two-motive model highlighting two distinct, overlapping dynamic motivational orientations that were hypothesized to interact with a MT to yield motive-aligned psychological benefits--a "distress reduction" motive and a "wellbeing enhancement" motive. Two research questions were investigated using different methodological approaches. RQ1 was investigated using an intent-to-treat (ITT) analytic framework, focusing on treatment versus waitlist control group comparisons within a single sample (n = 58) to determine whether motives interacted with a MT to yield motive-aligned benefits. RQ2 shifted to a treatment-on-treated (ToT) framework, focusing on teachers in the treatment condition across the three datasets (n = 83) to determine whether motives predicted motive-aligned benefits. Data were analyzed using structural equation modeling and post-hoc analyses were performed to further clarify results. Findings suggested that teachers' motives for participation mattered when it came to the benefits derived from a MT, but not in the manner hypothesized. Instead, RQ1 results showed that teachers who reported low motives (regardless of motive type) reported the greatest training benefits, while teachers who reported high motives reported either no benefits or even adverse change in psychological health outcomes. RQ2 results showed that teachers who started the MT with higher motives for participation also experienced the least benefits, and in some cases those teachers who reported higher motives also reported adverse change in psychological health outcomes. Together, these findings suggest that higher motivation to participate may signal the presence of other psychological states that make it more difficult to benefit from MTs, and that lower levels of motivation may signal psychological states that make it easier to benefit. Implications for theory and practice are discussed, including how this dissertation contributes to the theoretical advancement of existing frameworks by elucidating the role of motivation and motives in mindfulness trainings, and particularly helps to move forward theory and research on the mechanisms through which mindfulness training may have dissociable, predictable effects. A discussion of implications for practice includes recommendations for how future teacher MT programs might be adapted to better meet teachers' heterogeneous needs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]