Introduction The coronavirus disease 2019 (COVID‐19) pandemic has created an unprecedented global health crisis. Aim To investigate the impact of the 1st COVID‐19 lockdown on haemophilia patients in terms of symptoms, management, medication adherence, mental health and lifestyle behaviours. Methods A prospective cross‐sectional phone survey using a two‐part questionnaire was conducted in haemophilia patients (adults and children) followed‐up in a French Haemophilia Comprehensive Care Centre between May 5, 2020 and June 2, 2020 (CLEO CD study: NCT04390126). Results Among 284 haemophilia A or B patients with FVIII or FIX < 40% contacted for the study, 239 (84%) including 183 adults and 56 children participated to the survey. In 81% of children and 78% of adults, bleeding episodes remained unchanged or decreased. Medication adherence was 82.0% in adults and 98.2% in children. Non‐adherence concerned haemostatic agents in six patients and analgesics in three. Overall, 67% of adults and 71% of children felt as good as before lockdown. In both adults and children, the three major changes in lifestyle behaviours were: increase in screen time (49% and 57%), decrease in physical activity (43% and 48%), and weight gain (32% and 27%), respectively. Conclusions Encouraging results were observed in terms of haemophilia symptoms, medication adherence, and mental health. Conversely, a negative impact was observed on lifestyle behaviours in a cohort of French haemophilia patients during the 1st lockdown.