Nonattachment is a Buddhism-rooted construct, which can be defined as the relative absence of fixation on ideas, images, or sensory objects, as well as an absence of internal pressure to get, hold, avoid, or change circumstances or experiences. The present study was aimed at exploring the psychometric properties of the Spanish version of the Nonattachment Scale (NAS) and at delimitating the relationship between the NAS and measures of mindfulness, decentering, and negative emotional symptoms. Pooling the NAS data from Spanish meditators (n = 335) and nonmeditators (n = 270), we performed an exploratory factor analysis and then estimated the fit of two competing models (one-factor model vs. one-factor model + method effects) via confirmatory factor analysis. Data analyses showed that the Spanish version of the NAS is unifactorial in nature and has excellent internal consistency. As expected, high (positive) significant correlations were found between NAS and mindfulness and decentering measures, as well as high significant (negative) relations between NAS and depression, anxiety, and stress scores. Positive relations were also observed between NAS and variables of meditation practice. Large differences among the meditative, nonmeditative, and clinical groups (n = 39 patients with borderline personality disorder) were observed regarding NAS scores. Scores on the NAS were significant predictors of negative emotional symptoms (depression, anxiety, and stress) and, especially, resilience. Furthermore, NAS provided a unique contribution in the regression models, going beyond mindfulness facets and decentering. In conclusion, the Spanish version of the NAS is a psychometrically sound instrument with a promising future in the field of mindfulness and meditation research and in clinical settings.