The BCL2 inhibitor venetoclax is transforming the management of patients with chronic lymphocytic leukemia (CLL), given its high efficacy in relapsed/refractory CLL as observed in both early-phase and randomized clinical trials. The present study aimed to determine whether venetoclax is effective and well tolerated in patients with CLL or Richter’s syndrome (RS) in a real-world setting and to highlight factors impacting survival. Data from a venetoclax French compassionate use program were collected for 67 patients (60 with CLL and 7 with RS). Most patients presented adverse genetic features, such as TP53 disruption (74%) or complex karyotype (58%). Tumor lysis syndrome was observed in 14 (22%) patients, and 16 (24%) patients were hospitalized for grade III/IV infection. In the CLL cohort, ORR was 75 %, 1-year PFS was 61% (95% CI = 47–72%) and 1-year OS 70% (95% CI = 56–80%). No impact of TP53 disruption was noted while complex karyotype was identified as a predictor of both inferior PFS (HR = 3.46; 95% CI = 1–12; log-rank p = 0.03) and OS (HR = 3.2; 95% CI = 0.9–11.4, log-rank p = 0.047). Among the seven patients with RS, two achieved an objective response to venetoclax; however, the median OS was only 1.1 month. The well-balanced safety/efficacy profile of venetoclax is confirmed in this real-world setting. Complex karyotype should be evaluated as a predictive factor of survival for patients treated by venetoclax.