Background: Early treatment and strong family support are vital in determining stroke recovery outcomes. Family involvement facilitates early recognition of symptoms, timely access to care, and adherence to rehabilitation. However, evidence regarding their combined influence on post-stroke severity remains limited. Objectives: This study aimed to examine the relationship between family support and treatment timeliness with the level of post-stroke severity among patients treated at Sultan Agung Islamic Hospital, Semarang, Indonesia. Methods: A quantitative cross-sectional study was conducted involving 110 post-stroke patients selected through purposive sampling. Family support was measured using the Family APGAR questionnaire, treatment timeliness through a structured questionnaire, and stroke severity using the National Institutes of Health Stroke Scale. Data were analyzed using the Gamma correlation test and ordinal logistic regression. Results: Significant relationships were found between family support and stroke severity (p = 0.001; r = - 0.707) and between treatment timeliness and stroke severity (p = 0.001; r = 0.767). Regression analysis showed that treatment timeliness had a stronger effect on stroke severity (p < 0.001), while family support was not significant when both variables were included simultaneously in the model. Conclusions: Both family support and early treatment influence post-stroke severity, with treatment timeliness being the most dominant factor. Implications for Nursing: Nurses should strengthen family education programs to enhance early symptom recognition and rapid decision-making during stroke emergencies. Family empowerment and timely medical response can improve recovery outcomes and reduce post-stroke complications.