This study aims to compare the perceptions of nurses and families on the needs of the relatives of the patients in Intensive Care Unit (ICU). Methods:This cross-sectional study was conducted in the ICU of a university hospital. The study comprised 213 critical care patients' relatives and 54 nurses working in the same ICU. Data were collected using the Turkish version of Critical Care Family Needs Inventory (CCFNI) and a questionnaire on the characteristics of the participants. The difference between the perceptions of families and nurses was analyzed using Student t-test. Results: CCFNI's assurance/proximity subscale mean scores ranked first among both patients and nurses. The item "To be assured the best care possible is being given to the patient" was the top priority for both groups. Mean assurance/proximity and information dimensions of relatives were significantly higher compared to nurses (p <0.001). No significant difference was found between the perception of patient relatives and nurses related to support and comfort dimensions (p>0.05). Conclusion:Patient' relatives needs are underestimated by nurses. This inhibited the performance of ICU nurses in line with the holistic care approach. Educational objectives that include the needs of ICU patients' relatives should be incorporated into the undergraduate and in-service training of nurses. Policies should be established to create space and time for effective relative-nurse communication.