Background: Gender-related bias and discrimination have been well documented, particularly in male-dominated fields such as surgery, and have been associated with increased risk for physician burnout. In hematology/medical oncology, women make up between 41% and 49% of first-year fellows, but represent less than 40% of the academic hematology/oncology workforce. We aimed to study current hematology/oncology fellow perceptions about gender-related bias and challenges to inform interventions that promote gender equity. Methods: An anonymous 18-question survey was sent online to 165 adult and 75 pediatric hematology/oncology fellowship programs. Two group comparisons to analyze survey responses between genders were performed using chi-square, or Fisher’s test (if cell counts < 5), and Wilcoxon Rank Sum tests. Results: A total of 133 fellows completed the survey, where 88 self-identified as female (66%) and 45 (33.83%) self-identified as male. Most participants were White (52%), followed by Asian (29%), Hispanic (9%), Middle Eastern (5%), and Black (3%). Most respondents (n = 100; 75%) were age 31-40 years. More than half (54%) were enrolled in adult hematology/oncology fellowships, 24% were enrolled in pediatric hematology/oncology fellowship programs, and 88% practiced in University-based programs. Compared to male respondents, female fellows were more likely to report experiencing gender bias (p < 0.001), felt more insecure in their job (p = 0.043), felt second-guessed by colleagues (p < 0.001), and were more likely to believe that they had been unfairly denied a promotion (p = 0.003). In addition, female respondents were more likely to report having been mistaken as a non-physician (p < 0.001) and were more concerned about perceived gender bias. Female respondents reporting gender bias used techniques such as wearing a white coat (p < 0.0001), emphasizing a professional look (p < 0.0001), and ensuring “Doctor” (p < 0.0001) was clearly written on their badge more often than male fellows. When asked about how to combat gender-related challenges, female fellows more often recommended formal lectures and instruction about gender bias for attending physicians and non-physician staff. Suggestions about mitigating gender-related bias included encouraging same-sex mentors and open discussions about existing bias. Conclusions: Female hematology/oncology fellows reported facing gender-related bias and challenges in daily practice and often used specific techniques to face these challenges. Transparency and directed education about gender bias may help mitigate these challenges to create better working environments for fellows.