Background: Mindfulness training (MT) includes a variety of contemplative practices aimed at promoting intentional awareness of experience, coupled with attitudes of non-judgment and curiosity. Following the success of 8-week, manualized, group interventions, MT has been implemented in a variety of modalities, including smartphone applications that seek to replicate the success of group interventions. However, while smartphone apps are scalable and accessible to a wider swath of population, their benefits remain largely untested. Objective: The present study investigated a newly developed MT application called Wildflowers, which was co-developed with the lab for use in mindfulness research. It was hypothesized that MT through this application would improve subjective well-being, attentional control, and interoceptive integration, albeit with weaker effects than those published in the group intervention literature. Methods: Undergraduate students completed 3-weeks of MT with Wildflowers (n = 45), or 3-weeks of mathematical problem-solving training with a game called 2048 (n = 41). State training effects were assessed through pre-and post-session ratings of current mood, stress level, and heart rate. Trait training effects were assessed through pre-and post-intervention questionnaires canvassing subjective well-being, and behavioural task measures of attentional control and interoceptive integration. State and trait training data were analyzed in a multilevel model, using emergent latent factors (acceptance, awareness, openness) to summarize the trait questionnaire battery.