Background :Non-pharmacological, psychospiritual interventions for breast cancer patients remain underexplored in the Indonesian context, particularly interventions that structurally combine dhikr (remembrance of God) and tadabbur (reflective contemplation) of Qur’anic verses. Objective : This study aimed to evaluate the effectiveness of mindfulness therapy in improving the quality of life of breast cancer patients at Raden Mattaher Regional Hospital, Jambi City. Methods : The study used a quantitative quasi-experimental pretest-posttest control group design, involving 36 respondents (18 in the intervention group, 18 in the control group) selected through purposive sampling. Quality of life, assessed through its spiritual well-being dimension, was measured using the FACIT-Sp-12 questionnaire before and after two weeks of therapy. Data were analyzed using the Wilcoxon and Mann-Whitney tests. Results : Results showed that the mean quality-of-life score in the intervention group increased from 35.41 (SD 6.413) to 44.65 (SD 2.178) (p<0.001), while the control group increased from 32.56 (SD 3.258) to 39.33 (SD 2.223) (p<0.001). However, the Mann-Whitney test on the difference in scores between groups showed no significant difference (p=0.140). Conclusion : It was concluded that mindfulness therapy has the potential to improve the quality of life of breast cancer patients, although it has not yet been statistically proven superior to standard care. Further research with a larger sample and a longer intervention duration is recommended to strengthen the evidence of its effectiveness.