11090 Background: Growing evidence and NAPBC guidelines support the need for physical and/or occupational therapy (PT/OT) to optimize recovery from surgery. Research is needed to better understand the benefits of prehab (PT/OT before surgery and continuing afterward). We performed a retrospective study to understand the effect of participating in prehab or rehab-only on outcomes after surgery. Methods: Outpatient medical record data was extracted for cases who attended prehab (n=328) or rehab-only (n=306). Outcomes were upper extremity disability (Quick-DASH) and HRQOL (PROMIS measures of physical functioning, social role functioning, and global health [physical and mental]). Outcome time points included the post-surgery PT/OT assessment (T1, M=4 weeks), and PT/OT re-assessment (T2, M=15 weeks). We used linear mixed-effect models to examine the effect of prehab on T1/T2 outcomes while controlling for covariates (age, PT/OT, payer, and time), and to examine changes in outcomes from T1 to T2 for both groups. Results: Attending prehab was associated with better outcomes at T1 (upper extremity disability, p<.001; physical functioning, p<.001; social role functioning, p<.001; and physical health p<.001) and T2 (upper extremity disability, p=.025; physical functioning, p=.045; and social role functioning, p=.028; Table). From T1 to T2, each group improved significantly: upper extremity disability (prehab: M∆=8.92, p<.001; rehab-only: M∆=17.65, p<.001), physical functioning (prehab: M∆=1.89, p<.001; rehab-only: M∆=3.51, p<.001), social role functioning (prehab: M∆=1.61, p=.009; rehab-only: M∆=3.66, p<.001), and physical health (prehab: M∆=1.73, p<.001; rehab-only: M∆=3.50, p<.001). There was no significant effect of prehab on mental health and improvement from T1 to T2 was non-significant for both groups (p>0.05). Conclusions: In this study, attending outpatient prehab PT/OT services was associated with less upper extremity disability and greater HRQOL after breast cancer surgery. After post-surgery PT/OT, prehab and rehab-only cases each improved significantly; and upper extremity disability, physical functioning and social role functioning remained better among prehab cases. Although more research is needed, these findings support the integration of PT/OT in routine care and suggest that early PT/OT may optimize outcomes. [Table: see text]