Purpose To evaluate the diagnostic utility of the stalk and the inchworm sign on preoperative MRI for detecting superficial bladder cancers, and to compare the diagnostic performance between the stalk and the inchworm sign. Materials and Methods We retrospectively reviewed 240 patients (505 tumors) who had undergone radical cystectomy. The tumors were classified as follows: superficial or invasive tumors indicated by the stalk or inchworm sign on 3.0 Tesla MRI. We evaluated the diagnostic accuracy of the stalk and inchworm signs, by comparing each finding with the postoperative pathologic T stage. We compared diagnostic performance between them statistically. Results The stalk and inchworm signs showed high specificity (93% and 91%, respectively), positive predictive values (89% and 90%, respectively), and acceptable accuracy (70% and 74%, respectively), but low sensitivity (54% and 61%, respectively) and negative predictive values (60% and 63%, respectively). There was no statistically significant difference between the two signs (p > 0.05). Conclusion Superficial bladder cancers could be differentiated from invasive tumors using the stalk or inchworm sign on MRI.