These days, there are substantial number of papers published on the effects of meditation-based programs adapted for westerners involving different practices oriented toward mental and physical health. The study assessed the effects of a retreat which was solely focused on Shamatha practices (basic traditional Buddhist meditation practices). The participants on the retreat included those with 1 year of meditation practice or less (LP) and those with more than 1 year of meditation practice (MP). The objective of this study was to evaluate whether a traditional 9-day Shamatha Buddhist meditation retreat could change attention, mindfulness, and self-compassion levels in these participants. We also decided to investigate whether a meditation retreat, which could be intensive and exhaustive for beginners, could be equally beneficial for both LP and MP. The participants answered questionnaires before and after the retreat: Mindful Awareness Attention Scale (MAAS), Self-Compassion Scale (SCS), digit-symbol test, analog scales about stress, anxiety, frustration, perception and attention, and a question about their level of Shamatha based on a traditional Buddhist text. Participants showed improvements on most of the questionnaires and scales after the retreat. There were interaction effects (time and group) in perception (analog scale) and mindfulness. This study suggests that a traditional Shamatha retreat can improve mindfulness, attention, and self-compassion levels in the participants, irrespective of their experience. It also suggests that this kind of retreat could improve mindfulness and perception in participants with more than 1 year of meditation practice.