Mobile Assessment and Treatment for Schizophrenia (MATS) employs ambulatory monitoring methods and cognitive behavioral therapy interventions to assess and improve outcomes in consumers with schizophrenia through mobile phone text messaging. Three MATS interventions were developed to target medication adherence, socialization, and auditory hallucinations. Participants received up to 840 text messages over a 12-week intervention period. Fifty-five consumers with schizophrenia or schizoaffective disorder were enrolled, but 13 consumers with more severe negative symptoms, lower functioning, and lower premorbid IQ did not complete the intervention, despite repeated prompting and training. For completers, the average valid response rate for 216 outcome assessment questions over the 12-week period was 86%, and 86% of phones were returned undamaged. Medication adherence improved significantly, but only for individuals who were living independently. Number of social interactions increased significantly and a significant reduction in severity of hallucinations was found. In addition, the probability of endorsing attitudes that could interfere with improvement in these outcomes was also significantly reduced in MATS. Lab-based assessments of more general symptoms and functioning did not change significantly. This pilot study demonstrated that low-intensity text-messaging interventions like MATS are feasible and effective interventions to improve several important outcomes, especially for higher functioning consumers with schizophrenia.