•This study evaluates the prognostic value of VR-12 MCS on MIS-TLIF outcomes.•VR-12 MCS < 50 reported significantly inferior scores in all PROMs preoperatively.•MIS-TLIF patients with VR-12 MCS < 50 reported inferior postoperative outcomes.•VR-12 MCS < 50 reported greater rates of clinical improvement in mental health.•VR-12 MCS < 50 does not limit postoperative improvement in MIS-TLIF patients. No study has examined the prognostic value of the Veterans RAND-12 (VR-12) Mental Component Score (MCS) on postoperative outcomes in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) patients. This study examines the effect of preoperative VR-12 MCS on postoperative patient-reported outcome measures (PROMs) in MIS-TLIF patients. Patients were separated into 2 cohorts: VR-12 MCS < 50 and VR-12 MCS ≥ 50. PROMs of VR-12 MCS/Physical Component Score (PCS), Short Form-12 (SF-12) MCS/PCS, Patient-Reported Outcomes Measurement Information System-Physical Function (PROMIS-PF), Patient Health Questionnaire-9 (PHQ-9), Visual Analog Scale (VAS) Back/Leg Pain (VAS-BP/LP), and Oswestry Disability Index (ODI) were collected.Of 329 patients, 151 were in the VR-12 MCS < 50 cohort. The VR-12 MCS < 50 cohort reported significantly inferior scores in all PROMs preoperatively, significantly inferior VR-12 MCS, SF-12 MCS, PROMIS-PF, PHQ-9, and ODI scores at 6-weeks postoperatively, and significantly inferior scores in all PROMs, except for VAS-BP at final follow-up. Magnitude of 6-week postoperative improvement was significantly greater in the VR-12 MCS < 50 cohort for VR-12 MCS, SF-12 MCS, and PHQ-9. Magnitude of final postoperative improvement was significantly greater in the VR-12 MCS < 50 cohort for VR-12 MCS, SF-12 MCS/PCS, and PHQ-9. MCID achievement rates were significantly greater in the VR-12 MCS < 50 cohort for VR-12 MCS, SF-12 MCS, and PHQ-9. MIS-TLIF patients with lesser preoperative VR-12 MCS reported inferior postoperative outcomes in mental health, physical function, pain, and disability. However, patients with inferior preoperative mental health reported greater rates of clinically meaningful improvement in mental health. Inferior preoperative mental health does not limit postoperative improvement in patients undergoing MIS-TLIF.