Background and Objective: Critical illnesses and subsequent hospitalization of a relative in an intensive care unit (ICU) leading many psycho-social stresses for patients and their family members. Managing of the stress among families is an integrate part of critical care nursing. Therefore, this study was conducted to determine the effects of a programmed education, provided during the first few days of patient's hospitalization on stress of the family carers in Isfahan hospitals of medical science university.   Material and Methods: This is a quasi- experimental study, performed on 96 primary family members of each critically ill patient who had been newly admitted to Isfahan hospitals recruited by a sequential random sampling over a period of three months. All of patient's family were trained psychosocial need-based to alleviate their stresses by an ICU nurse. Stress levels and scores were measured and compaired before and after education, using a three part questionnaire, including demographic, critical care family need inventory (CCFNI) and stress. The third part of questionnaire was designed based on the IES and DASS questionnaires. Tests of T and ANOVA were used by SPSS software, for data analysis.  Results : Our results showed that, the mean family psychosocial need scores of the before and after education were 65.44 ± 2.6 and 42.43 ±3, respectively, with a significant difference (p=0.000). T he majority family psychosocial need levels of the before education were (70.7%) , and the after education were (100%) needs with a significant difference (p=0.000). M ost significant family reported is the need for information (90.7 ±6.3 ) for supportative (75.2 ±5.5 ) and proximity (67.7 ±6.3 ). Mean stress scores of the before and after education were 86.06 ± 9.7 and 43.3 ±6.8, respectively with a significant difference (p = 0.000). The level of stress before and after education was 98% and 92.7% respectively which the difference was significant (p=0.000).   Conclusion: The reduction of family stress in this study support the effectiveness of providing families of newly admitted critically ill patients, with a need based education intervention to reduce stress, Therefore, probably planned educational programmes for the family members regarding psychosocial needs by nurses are important. Findings of this study possibly serve as guidance for nurses in delivering competent interventions.