BACKGROUND: There is a gap in the extant literature regarding length of stay (LOS) in short-term inpatient addiction treatment facilities. Furthermore, there is a lack in focus on treatment factors which may be better indicators for positive patient outcomes than demographic profiles. The current study sought to examine modifiable correlates of LOS within a short-term inpatient residential facility to extend LOS and improve patient outcomes. METHODS: N = 792 participants who completed a baseline assessment and either completed treatment or left against clinical advice were included in the sample. Outcomes of interest were self-efficacy (domains included negative affect, pro-social or positive use, physical discomfort, withdrawal, or urges), well-being (domains included symptom distress, interpersonal relations, and social role), and social network size. RESULTS: Baseline dysfunctional social role, larger social network size, and higher alcohol use disorder (AUD) severity all led to increases in LOS. No aspects of self-efficacy, symptom distress, interpersonal relatedness, substance use disorder (SUD) severity, nor other demographic variables were associated with LOS. CONCLUSIONS: This study highlights the importance of taking steps to improve self-perceived social role and social network size. Given that the purpose of this study was to determine modifiable correlates of LOS, we suggest that clinicians at inpatient, short-term addiction treatment centers adopt thorough measures of well-being and social network to support patient treatment and recovery.