Background: Use of GA by oncology specialists is low in Mexico, with some of the domains of the GA more frequently assessed than others in everyday practice. We aimed to explore factors associated to the evaluation of individual GA domains by Mexican cancer care providers. Methods: Secondary analysis of a mixed-methods study which consisted of an online cross-sectional survey of Mexican oncology specialists and follow-up interviews on the use of GA in cancer care. We performed multiple logistic regression analyses with frequency of evaluation of specific GA domains as the dependent variable (dichotomized as never/sometimes vs most of the time/always). Independent variables included age, gender, medical specialty, and practice size of the survey respondent, presence of a geriatrician in main practice site, and perceived confidence in managing common situations in older adults relevant for each GA domain (dichotomized as not at all/mildly vs very/completely). A p-value of < 0.05 was considered significant in each model. Results: Of 196 survey respondents, 62% were male, 50% surgical oncologists, 51% took care of > 10 patients per day, and 61.7% had access to a geriatrician at their main practice site. Frequently (most of the time/always) evaluated domains included: comorbidities (94.4%), daily function (72.9%), nutrition (67.3%), cognition (54.1%), depression (42.9%) and falls (42.3%). Self-perceived confidence in managing dementia (OR 2.72; 95% CI 1.42-5.51, p = 0.008) and being a surgical oncologist (OR 2.80; 95% CI 1.29-5.72, p = 0.003) were associated with increased evaluation of cognition. For nutrition, only self-perceived confidence in nutritional evaluation was associated (OR 3.86; 95% CI 2.0-7.46, p < 0.001). For comorbidities, self-perceived confidence in managing osteoporosis (OR 5.61; 95% CI 1.03-30.4, p = 0.046). For falls, significant factors included age (OR 1.04; 95% CI 1.01-1.07, p = 0.004), practice size (OR 0.46; 95% CI 0.23-0.91, p = 0.026), and self-perceived confidence in evaluation and prevention of falls (OR 6.31; 95% CI 3.19-12.46, p < 0.001). Age (OR 1.03; 95% CI 1.01-1.06, p = 0.011) and self-perceived confidence in managing depression (OR 2.52; 95% CI 1.33-4.78, p = 0.005) were associated with evaluation of depression. For daily function, no variables were significantly associated. Follow-up interviews showed quality and appropriateness of evaluations may not be ideal, such as asking only about orientation and level of consciousness when evaluating cognition. Conclusions: Self-perceived confidence in evaluating and managing common situations in older adults is associated with the evaluation of GA domains as part of everyday practice among cancer care providers in Mexico. This analysis supports the use of educational interventions to boost knowledge and confidence regarding the proper use of validated GA tools among oncology specialists.