Substance use is a pervasive health problem. Therapeutic community (TC) is an established substance abuse treatment but TC environments are stressful and dropout rates are high. Mindfulness-based TC (MBTC) intervention was developed to address TC stress and support self-change that could impact treatment retention. Self-change was assessed through feeling and thinking word-use in written stories of stress from 140 TC residents in a historical control group and 253 TC residents in a MBTC intervention group. Data were collected 5 times over a 9-month period. Linguistic analysis showed no differences between the groups over time; however, over all time points, the MBTC intervention group used fewer negative emotion words than the TC control group. Also, negative emotion (P < .01) and anxiety (P < .01) word-use decreased whereas positive emotion word-use increased (P < .05) over time in both groups. Descriptive data from linguistic analyses indicated that sustained self-change demands participation in mindfulness behaviors beyond the instructor-guided MBTC intervention.