Background: Parents are profoundly affected by a child's cancer diagnosis. The study aimed to evaluate anxiety, depression, sleep quality and physical activity of mothers of children with leukemia. Material/Methods: The study involved 57 mothers of children with leukemia (91% lymphoblastic, 9% myeloid). The participants completed a questionnaire created for this study on basic sociodemographic data, Euro Quality of Life Questionnaire (EQ-5D), State-Trait Anxiety Inventory (STAI), Beck Depression Inventory (BDI), International Physical Activity Questionnaire (IPAQ), and Pittsburgh Sleep Quality Index (PSQI). Results: The mean raw score of the STAI (sheet X-1) was 43.91 +/- 10.44. Converted into sten (standardized 1-10 scores), the mean age of the study group was 5.45 +/- 2.03. The results of the questionnaire assessing depression symptom severity (BDI) was 14.25 +/- 9.11 in the study group, and the physical activity of the respondents, measured by the IPAQ, was 2010.82 +/- 2668.03 metabolic equivalent (MET) units. Physical activity was insufficient in 36.8% of respondents, sufficient in 35.09%, and high in 26.32%. According to PSQI, 36.84% of respondents had good sleep quality and 63.16% had poor sleep quality. The analysis found strong correlations between BDI score and EQ-5D (0.72; P<0.05), BDI and daytime dysfunction (PSQI subscale) (0.65; P<0.05), BDI and EQ-5D pain/discomfort (0.61; P<0.05), and BDI and EQ-5D anxiety/depression (0.61; P<0.05). Conclusions: Mothers of children diagnosed with leukemia tend to have poor mental health, including decreased quality of life, increased anxiety, depressive symptoms, and poor sleep quality, regardless of physical activity level.