Acquisition and generalization of specific behavioral skills is a key component of dialectical behavior therapy (DBT) for individuals with borderline personality disorder (BPD). We examined the feasibility, acceptability, usability, and immediate effects of the DBT Coach, a mobile phone application (app) designed specifically to augment skills generalization through interactive coaching in DBT skills. In this pilot study, we provided the DBT Coach installed on a mobile device as an adjunct to 6 months of standard DBT, among a sample of 16 individuals with BPD and a recent history of attempted suicide and/or nonsuicidal self-injury (NSSI). Results indicate good acceptability and usability of the DBT Coach with considerable between-person variability in the frequency of app use and a median use of only 11.5 times over the course of treatment and a 3-month follow-up period. Using a hierarchical linear modeling approach, analyses indicated the DBT Coach reduced subjective distress and urges to self-harm following app use. However, use of the DBT Coach was not related to any treatment outcomes, except for reductions in NSSI. This study is the first to examine the use of mobile technology as an adjunct in DBT and highlights some potential challenges in incorporating apps into treatment. Implications for future research and clinical utility are discussed.