One Day of Coaching: Effectiveness of a SystemicConstructivist Coaching ApproachAbstract Using an exploratory approach, the influence of coaching (based on the SKETM model) on a number of results indicators was examined. SKETM stands for "systemisch-konstruktivistisches Einzel-und Teamcoaching im Management", i. e. systemic-constructivist individual and team coaching in management. The main features of coaching based on the SKETM model are the coach guiding the process, making everything transparent to the client, while concurrently refraining from interfering/mingling with the content. Coachings based on the SKETM method last for one day.The study employed a quasi-experimental wait-list design with measures at time 0, time 1 and time 2. Out of a total of 64 coachees at time 0, a number of 33 were assigned to the wait-list control group and 31 to the intervention group. 25 coaches, all working with the SKETM method, participated in the study. The following results indicators were used: a goal attainment scale, a coaching evaluation questionnaire -(Fragebogen Evaluation Coaching -Klärung und Umsetzung des Anliegens FEC-KU); and parts of the incongruence questionnaire INK. Interaction and time effects were evaluated using generalized estimating equation (GEE).Significant time effects (t0-t2) and small to large effects for all scales ( Coaching based on the SKETM model is an effective intervention method, contributing to goal attainment, problem clarification and solving as well reducing the incongruence perception in a number of issues. The measured effects are equal or higher in comparison to the values obtained in previous meta-analyses on the effectiveness of coaching.First quasi-experimental field study on systemic-constructivist coaching.