Abstract Background: Mailed fecal immunochemical test (FIT) outreach can improve colorectal cancer screening participation. We assessed the reach and effectiveness of adding notifications to mailed FIT programs. Methods: We conducted secondary analyses of a stepped-wedge evaluation of an enhanced mailed FIT program (n = 15 clinics). Patients were stratified by prior FIT completion. Those with prior FIT were sent a text message (Group 1); those without were randomized 1:1 to receive a text message (Group 2) or live phone call (Group 3). All groups were sent automated phone call reminders. In stratified analysis, we measured reach and effectiveness (FIT completion within 6 months) and assessed patient-level associations using generalized estimating equations. Results: Patients (n = 16,934; 83% Latino; 72% completed prior FIT) were reached most often by text messages (78%), followed by live phone calls (71%), then automated phone calls (56%). FIT completion was higher in patients with prior FIT completion versus without [44% (Group 1) vs. 19% (Group 2 + Group 3); P < 0.01]. For patients without prior FIT, effectiveness was higher in those allocated to a live phone call [20% (Group 3) vs. 18% (Group 2) for text message; P = 0.04] and in those who personally answered the live call (28% vs. 9% no call completed; P < 0.01). Conclusions: Text messages reached the most patients, yet effectiveness was highest in those who personally answered the live phone call. Impact: Despite the broad reach and low cost of text messages, personalized approaches may more successfully boost FIT completion.