This article explores mindfulness skills in community and borderline personality disorder (BPD) samples. Study 1 includes 173 community volunteers and explores the psychometric properties of the French version of the Kentucky Inventory of Mindfulness Skills (KIMS). Study 2 explores the KIMS factor structure in 130 BPD patients and compares KIMS scores of this sample with those of the community sample from Study 1. Study 3 investigates the changes in KIMS scores in a BPD sample (n = 82) treated with Intensive Dialectical Behavior Therapy (I-DBT). Results suggest that the psychometric properties of the French KIMS are comparable with those of the original version in the community and the BPD samples. Moreover, fewer mindfulness skills were found in BPD patients than in control participants. It was also observed that the ability to describe and to act with awareness increased in BPD patients after I-DBT. The present work makes a French instrument measuring mindfulness in daily activities available for clinical practice and research.