PURPOSE To describe perceptions of infertility risk among adult survivors of childhood cancer, to test the concordance of survivors’ risk perceptions and their adult fertility status, and to identify explanatory factors (sociodemographic factors, gonadotoxic treatments, reproductive history, sexual dysfunction) associated with these outcomes. PATIENTS AND METHODS Adult childhood cancer survivors (N = 1,067; without children or a history of pregnancies) completed questionnaires that asked about infertility risk perceptions and participated in physical evaluations, including biomarkers of gonadal functioning (eg, semen analysis, blood hormone levels, menses). Multivariable regression models tested associations between explanatory factors and risk perceptions as well as concordance of perceptions and fertility status. RESULTS Most childhood cancer survivors (61.9%) perceived themselves at increased risk for infertility, which was significantly associated with sociodemographic factors (older age, white ethnicity, being married/partnered, higher education), gonadotoxic treatments, fertility concerns, previous unsuccessful attempts to conceive, and sexual dysfunction (all P < .05). Laboratory-evaluated impaired gonadal function was found in 24.3% of female and 55.6% of male survivors, but concordance with survivors’ risk perceptions was low (Cohen’s κ < .19). Most survivors with discordant perceptions overestimated risk (ie, perceived being at risk, though fertility status seemed normal; 19.7% of male and 43.6% of female survivors), whereas a minority underestimated risk (ie, perceived no risk but were impaired/infertile; 16.3% of male and 5.3% of female survivors). Factors related to discordance included sociodemographics, gonadotoxic treatments, fertility concerns, and sexual dysfunction (all P < .05). CONCLUSION Although childfree survivors may correctly consider themselves at risk for infertility on the basis of their previous treatments, such risk perceptions were discordant from laboratory-evaluated fertility status among many survivors in adulthood. Thus, repeated fertility-related communication throughout survivorship is essential, because treatment-indicated risk does not equal fertility status after treatment. Offering fertility testing to those who were at risk and/or those with fertility-related concerns is recommended.