Background: Delay in time to treatment initiation (TTI) has been shown to independently and adversely affect disease-specific mortality in patients with different cancers. Social Determinants of Health (SDoH) are increasingly recognized as significant contributors to patients’ disease management and health outcomes. Our academic center has developed and validated a 10-item SDoH screener that has been in place since 2018. We evaluated which self-reported social needs may be predictive of delayed TTI. Methods: This is a retrospective cohort study at an urban community-based academic center of patients diagnosed with breast, colorectal, endocrine and neuroendocrine, gastrointestinal, genitourinary, gynecologic, head and neck, hematologic, hepatobiliary, lung, and pancreatic cancer from August 2018 to September 2022. We identified patients who had completed an SDoH screening and had diagnosis and treatment data in the hospital’s cancer registry. Variables of interest included median household income (based on home zip code and US Census data), area deprivation index (ADI) (based on the Neighborhood Atlas from the University of Wisconsin), Charlson Comorbidity Index (CCI) score, marital status, smoking history, insurance status, tumor stage, and emergency department (ED) or inpatient admission 30 days before diagnosis. Factors associated with TTI delay, defined as TTI ≥ 45 days, were assessed using multivariable logistic regression. Results: Among 2,328 patients (66.6% female, 43.4% Hispanic, 35.7% Black, and 9.4% White), the median age was 65 (IQR, 56-73) and the median TTI was 25 days (IQR, 0-51 days). The multivariable models showed that patients with one or more self-reported unmet social needs experienced a statistically significant delay in TTI (odds ratio [OR], 1.68; 95% CI, 1.54-1.82). The disparities most strongly associated with delay were legal help, healthcare transportation, housing stability, and the need to provide care for others. Additionally, patients identified as non-Hispanic Black (OR, 1.44; 95% CI, 1.32-1.57) or Hispanic (OR, 1.47; 95% CI, 1.19-1.50) were more likely to have a delay compared to non-Hispanic White patients. A decreased likelihood for delayed TTI was found in those with ED (OR, 0.49; 95% CI, 0.44-0.54) or inpatient (OR, 0.54; 95% CI, 0.50-0.58) admission 30 days before diagnosis. Conclusions: Our data show that delays over 45 days are independently associated with unmet social needs. Additionally, ED or inpatient admissions within 30 days before diagnosis help increase care coordination and compliance, leading to improved TTI. These findings suggest that cancer patients who have unmet social needs are at higher risk of treatment delay and may benefit from interventions to mitigate needs, especially legal, transportation, and housing assistance.