The Mindful Attention Awareness Scale (MAAS) measures perceived degree of inattentiveness in different contexts and is often used as a reversed indicator of mindfulness. MAAS is hypothesized to reflect a psychological trait or disposition when used outside attentional training contexts, but the long-term test–retest reliability of MAAS scores is virtually untested. It is unknown whether MAAS predicts psychological health after controlling for standardized socioeconomic status classifications. First, MAAS translated to Danish was validated psychometrically within a randomly invited healthy adult community sample (N = 490). Factor analysis confirmed that MAAS scores quantified a unifactorial construct of excellent composite reliability and consistent convergent validity. Structural equation modeling revealed that MAAS scores contributed independently to predicting psychological distress and mental health, after controlling for age, gender, income, socioeconomic occupational class, stressful life events, and social desirability (β = 0.32–.42, ps < .001). Second, MAAS scores showed satisfactory short-term test–retest reliability in 100 retested healthy university students. Finally, MAAS sample mean scores as well as individuals’ scores demonstrated satisfactory test–retest reliability across a 6 months interval in the adult community (retested N = 407), intraclass correlations ≥ .74. MAAS scores displayed significantly stronger long-term test–retest reliability than scores measuring psychological distress (z = 2.78, p = .005). Test–retest reliability estimates did not differ within demographic and socioeconomic strata. Scores on the Danish MAAS were psychometrically validated in healthy adults. MAAS’s inattentiveness scores reflected a unidimensional construct, long-term reliable disposition, and a factor of independent significance for predicting psychological health.