Purpose The COVID-19 pandemic and the extended lockdown are associated with numerous changes in behavior and lifestyles. The objective was to assess the impact of the first lockdown on LBP course among chronic LBP patients. Methods Descriptive and analytical, cross-sectional, multicenter study, conducted by questionnaire from mid-May to end of June 2020 among patients treated for chronic LBP in 6 French and 1 Swiss center. Collected data concerned changes in LBP intensity during lockdown, lockdown experience, physical activity (PA) practice and sedentary lifestyle prior and during lockdown, recourse to care, consumption of psychoactive substances for LBP, and professional activity and its conditions during lockdown. Results 360 participants (58.6% women, 52.1 ± 13.4 years) were included of which 65% were active (63% keep on working of which 54% teleworked). LBP got worse in 41.1%, mean VAS went from 49.5 ± 21.6 before to 53.5 ± 22.4 during lockdown (p < 0.001) and needed increase of treatment by 29% but very few people increased their consumption psychoactive substances for analgesia. Half of participants had well-experienced lockdown. Findings revealed a significant decrease in PA and increase of sedentary during lockdown (p < 0.0001). Good experience of lockdown was associated with LBP improvement (OR = 0.6 [0.3-0.9]) and decrease of PA with LBP worsening (OR = 1.9 [1.1-3.2]). Teleworking was also associated with LBP worsening. Gender, age, or BMI did not influence LBP course. Conclusion These findings indicate that chronic LBP people suffered from increase in self-perceived LBP during lockdown and help to better understand the factors associated with their condition.