Chronic low back pain (cLBP) is a highly prevalent and disabling health condition. Identifying risk factors and resources for low back pain (LBP) and back health in everyday life is crucial for its prevention and management. This study examined moment‐to‐moment fluctuations in pain intensity and perceived back health and their associations with fear of movement, pain self‐efficacy, and leisure‐time physical activity in individuals with (n = 128) and without (n = 94) cLBP. Data were collected five times per day for 14 days (nmeasurements = 13,292). Participants with cLBP reported experiencing LBP in 45% of all measurements, with a mean intensity of 3.16 (range: 1–9), whereas participants without cLBP reported LBP in 6.9% of measurements (Mintensity = 2.38). Multilevel analyses including participants with and without cLBP showed that greater momentary fear of movement, lower momentary pain self‐efficacy, and higher momentary levels of leisure‐time physical activity were associated with higher pain intensity (β = .05, p = .042, β = −.15, p < .001, and β = .04, p = .001). Greater momentary fear of movement and lower momentary pain self‐efficacy were associated with poorer back health (β = −.07, p = .004 and β = .16, p < .001). The observed within‐person associations highlight the potential for ecological momentary interventions targeting modifiable psychological factors related to cLBP in daily life, particularly pain self‐efficacy.
