Aim: To investigate the effects of nursing interventions based on Mishel’s Uncertainty in Illness Theory (MUIT) on uncertainty, hopelessness, coping with and adaptation for caregivers of children diagnosed with cancer. Materials and Methods: The study was a randomized controlled experimental design study, which had repeated measures (pretest-posttest-follow up) and parallel group (intervention-control), and it included measures of uncertainty (PPUS), hopelessness (BHS), coping with and adaptation (CAPS). The study was conducted in January-July 2019 with the caregivers of 46 (Intervention Group: 23; Control Group: 23) children diagnosed with cancer and followed in paediatric oncology-haematology clinics. Intervention Group (IG) was given 6 modules education and consultancy according to protocol that was developed based on theory. The CONSORT guideline was performed in the study. The data of the research were evaluated by using descriptive statistics, Chi-squared test, independent samples t-test, repeated measures two-way analysis of variance (ANOVA). Results: PPUS post-test mean score of IG was lower than CG (p<0.05), and perceptions of uncertainty decreased significantly over time depending on the caregivers being in the IG and CG (p<0.05). It was determined that BHS post-test and follow-up mean scores of IG was lower (less hopelessness perception) than the CG (p<0.05). CAPS’ post-test and the follow-up mean scores were similar in IG and CG. Also, Group*time effect on hopelessness, coping and adaptation perception was statistically similar, too. Conclusion: Nursing interventions based on MUIT can positively support caregivers’ uncertainty, hopelessness and coping adaptations.