Background: Empathy is the ability to put yourself in the place of others and understand their feelings and experiences. Empathy with cancer patients is essential in all disease stages. The purpose of our study was to determine the level and type of empathy in a sample of Iranian oncology nurses and to investigate the relationship between nurses' empathy and their demographic characteristics. Methods: This is a descriptive study with cross-sectional design, which was carried out by a convenience sample of oncology nurses (n = 181). They answered the Jefferson Scale of Empathy-Nursing Student version R (JSE-NS version R), and the Interpersonal Reactivity Index (IRI). Independent t-test and ANOVA were used to determine the difference of empathy based on various demographic variables. The relationship between empathy and significant demographic variables were evaluated by multiple linear regression (MLR) analyses. Results: The mean age of the oncology nurses was 34.9 ± 6.7 years. The mean score of empathy was 106 ± 16.5 (range of 20-140) using the JSE-NS version R. Based on the IRI subscales, the mean score of empathic concern (20.5 ± 5.8) was higher in comparison with the subscales of perspective-taking (14.6 ± 3.5), fantasy (11.0 ± 5.5), and personal distress (14.0 ± 4.5). MLR models showed that the variables of age (β = 0.22, p ≤ 0.005), marital status (β = 0. 21, p ≤ 0.006), and having children, (β = 0.19, p ≤ 0.012) predicted 22% of changes in the nurses' empathy, respectively. Discussion: This study showed that empathy is more emotional than cognitive in this sample of oncology nurses. As a cognitive response is more dependent on subjective judgments, there is a possibility to increase the level of this kind of empathy. Conclusions: Empowering oncology nurses is necessary in the field of cognitive empathy, by periodic measurements, and in-service training programs with focus on nurses' experiences.