Purpose: This study investigated the incidence of fatigue, insomnia, depression, anxiety, and stress symptoms in patients after allogeneic hematopoietic stem cell transplantation (AHSCT), as well as explored potential relationships among these symptoms. Methods: A total of 126 patients who had undergone transplantation at a university hospital at least one month prior to the study's commencement were included. The study was conducted as a cross-sectional and relational research, and data were collected using the "Personal Information Form," "Brief Fatigue Inventory," "Insomnia Severity Index," and "Depression Anxiety Stress Scale." Statistical analyses included descriptive statistics, parametric and nonparametric tests, and correlation analyses using the Spearman Correlation Coefficient. Additionally, mediation analyses were conducted using a Structural Equation Model to explore potential causal relationships among the variables. Results: The incidence of fatigue was high among patients, with 94% experiencing this symptom following transplantation. Additionally, 52% had anxiety, 47% had insomnia, 47% had depression, and 34% had stress. Moderate relationships were observed between these symptoms. Regression analysis revealed that one-point increase in fatigue was associated with increases in stress 1.065 points, depression 0.937 points, anxiety 0.956 points, and insomnia 0.138 points (p<0.001). Similarly, one-point increase in insomnia was associated with increases in fatigue 3.342 points, stress 0.972 points, depression 0.885 points, and anxiety 0.816 points (p<0.001). Conclusion: After AHSCT, fatigue was the most frequent symptom experienced by patients, followed by insomnia, depression, anxiety, and stress. There was a relationship between these symptoms. Additionally, evidence suggested that insomnia was more strongly associated with fatigue compared to the other symptoms.