Background: A randomized cross-over phase II trial (Lancet Oncol 20(12):1730, 2019) showed the sequence of AAP followed by ENZ is associated with a better time to PSA progression compared with the opposite sequence and superior 2^nd line activity of ENZ. It is unknown whether one treatment sequence is associated with better QOL than the other. Methods: 202 Patients were randomized (1:1) to receive either AAP followed by ENZ at PSA progression (arm A) or the opposite sequence of ENZ followed by AAP (arm B). FACT-P questionnaires were completed at baseline, cross-over and every 4 weeks on treatment. Time to QOL deterioration (TTQOLD) for the treatment sequence was determined from start of 1^st line treatment to first questionnaire with a clinically meaningful decrease from baseline and compared between arms using the log-rank test. TTQOLD was also determined for 1^st line and 2^nd line separately. The proportion of patients with QOL deterioration for total FACT-P score and FACT-P subscores from baseline to week 12 of 1^st and 2^nd line treatment was compared between arms using X² test. Results: Median follow-up for 1^st and 2^nd line and whole sequence were 9.3, 6.6 and 22.0 months (mos) respectively and questionnaire completion rate was 81%. TTQOLD for total FACT-P score for the whole sequence for arm A vs B was 10.5 mo (95% CI 5.0-15.5) vs 10.8 mo (5.5-13.1), p = 0.74. For 1st-line AAP vs ENZ, median TTQOLD was 15.5 mo (5.5-21.2) vs 11.0 (5.5-13.3) respectively (p = 0.23). For 2^nd line ENZ vs ABI, median TTQOLD was 3.7 mo (2.0-5.4) vs 5.8 (2.8-12.1), p = 0.13. There was a higher rate of deterioration in physical well-being (PWB) for 1^st line ENZ (arm B) and 2^nd line ENZ (arm A) (Table). Conclusions: There was no difference in TTQOLD between the two treatment sequences of AAP and ENZ. Although treatment with second line ENZ has been associated with greater anti-cancer effects, ENZ was associated worse PWB QOL scores. Clinical trial information: NCT02125357.