Abstract Background Due to the increasing prevalence of Kawasaki Disease (KD) in adulthood, the number of women considering pregnancy is growing. There are limited data on the course of pregnancy in KD with coronary artery involvement. Case summary We report on the pregnancy outcome of a 30-year-old woman with KD who was successfully resuscitated for ventricular tachycardia 3 years before. At that time, bypass surgery and later implantable cardioverter-defibrillator implantation were performed because of thrombotically occluded calcified giant coronary aneurysms. The pregnancy course was initially uncomplicated, however, at 31 weeks of gestation, left-sided breast cancer was diagnosed. Weighing maximum therapeutic efficacy against acceptable foetal and maternal cardiotoxic risk, our multidisciplinary team decided on neoadjuvant chemotherapy. The mother and foetus tolerated the therapy well. However, at 36 weeks of gestation, due to HELLP (haemolysis, elevated liver, low platelets) syndrome, a caesarean section had to be performed. The newborn was healthy with good APGAR (appearance, pulse, grimace, activity, respiration) scores. Three weeks after delivery, chemotherapy was restarted and at Week 4 after the caesarean section, the tumour was no more detectable. Discussion We discuss data on pregnancy and KD and outline that pregnancy can be considered if the clinical condition is good and left ventricular function is preserved. We also address possible therapeutic approaches and care for breast cancer in pregnancy and coexisting cardiovascular disease. The extraordinary importance of interdisciplinary cooperation between different disciplines in such complex clinical disease conditions is emphasized.