OBJECTIVES:  To investigate whether early improvements in patient-reported outcomes (PROs) observed with certolizumab pegol (CZP) treatment were maintained over 4 years in the RAPID-axSpA trial of axial spondyloarthritis (axSpA) patients, including ankylosing spondylitis (AS) and non-radiographic axSpA (nr-axSpA). METHODS:  The RAPID-axSpA trial (NCT01087762) was double-blinded and placebo-controlled to Week (Wk)24, dose-blinded to Wk48, and open-label to Wk204. Patients fulfilled ASAS criteria and had active axSpA. Patients originally randomized to CZP (200mg every 2 wks or 400mg every 4 wks) continued assigned dose in open-label period. Outcomes reported include total back pain, fatigue, BASFI, ASQoL, and Sleep Problems Index II domain of Medical Outcomes Study Sleep Scale (MOS-SPI). PRO data are reported for patients randomized to CZP at Wk0 (combined doses) as mean change from baseline, imputed by last observation carried forward. RESULTS:  Of 218 axSpA patients randomized to CZP at Wk0 (121 AS; 97 nr-axSpA), 203 (93%) completed Wk24 and 142 (65%) Wk204. Rapid improvements from baseline to Wk24 were maintained over 4 years (to Wk204) in total back pain (Wk24: -3.2; Wk204: -3.7), fatigue (Wk24: -2.7; Wk204: -3.1), BASFI (Wk24: -2.4; Wk204: -2.7), ASQoL (Wk24: -5.1; Wk204: -5.9), and MOS-SPI (Wk24: -12.8; Wk204: -14.6). Responses were similar in AS and nr-axSpA patients in all PROs assessed, including total back pain (Wk24: -3.2, -3.3; Wk204: -3.6, -3.8), fatigue (Wk24: -2.6, -2.9; Wk204: -3.0, -3.3), BASFI (Wk24: -2.3, -2.4; Wk204: -2.6, -2.7), ASQoL (Wk24: -4.8, -5.5; Wk204: -5.7, -6.3), and MOS-SPI (Wk24: -10.5, -15.7; Wk204: -12.7, -16.9; data shown for AS and nr-axSpA, respectively). Similar outcomes were also seen with both CZP dose regimens. CONCLUSIONS:  Early improvements in axSpA patients, observed to Wk24 in all PROs assessed, were subsequently maintained over 4 years of CZP treatment to Wk204. Similar maintained improvements were observed in both the AS and nr-axSpA subpopulations.