The time patients wait before seeking help for cancer symptoms is among the most important factors contributing to diagnostic delays in cancer. We reviewed the association between time to help-seeking and three psychological factors: symptom knowledge, symptom interpretation, and beliefs about cancer (Prospero review protocol CRD42018088944). Forty-seven studies published between 1990 and 2019 met the inclusion criteria, providing data on 44,961 participants from 22 countries concerning seven cancer sites. A series of random-effects meta-analyses and meta-regressions were conducted. Better symptom knowledge was related to lower odds of a long help-seeking interval in both studies with healthy populations (OR = .73, 95% CI [.63, .84], k = 19) and with patients (OR = .40, 95% CI [.23, .69], k = 12), and so was interpreting experienced symptoms as cancer-related (OR = .52, 95% CI [.36, .75], k = 13 studies with patients). More positive beliefs about cancer (i.e., that cancer is treatable) were associated with lower odds of a long help-seeking interval in both studies with healthy populations (OR = .70, 95% CI [.52, .92], k = 11) and with patients (OR = .51, 95% CI [.32, .82], k = 7). Symptom knowledge, interpretation, and beliefs about cancer are likely to be universal predictors of help-seeking. Theoretical models of patient help-seeking and interventions aiming to reduce delays should incorporate these factors.