The development of new one-pot sequential cyclizations involving a Vilsmeier–Haack reaction followed by an organocatalyzed Mannich reaction is reported. This synthetic strategy gives access to functionalized indolizidines and quinolizidines in one operation from readily synthesized precursors. Yields and diastereoselectivities are good to excellent when formamides are used to trigger the key step, bearing either an electron-rich aryl or a pyrrole as the nucleophilic partner in the first cyclization.