Most heteroaryl selenides and diselenides are biologically active, with some reported to act as antioxidants and show activities that are medicinally relevant; hence, the development of efficient methods for their synthesis is an important objective. Herein, a simple method for the synthesis of selenides and diselenides bearing imidazo[1,2-<italic>a</italic>]pyridine rings and their anticancer activity are described. The double C–H selenation of imidazo[1,2-<italic>a</italic>]pyridine with Se powder was catalyzed by CuI (10 mol %) ligated with 1,10-phenanthroline (10 mol %) at 130 °C under aerobic conditions. The selenides or diselenides were prepared almost selectively using selenium powder in an appropriate quantity under otherwise identical reaction conditions. The prepared selenides and diselenides bearing two imidazo[1,2-<italic>a</italic>]pyridine rings were all novel compounds. Among the prepared diselenides and selenides that exhibited cytotoxicity against cancer cells, bis[2-(4-methoxyphenyl)imidazo[1,2-<italic>a</italic>]pyridin-3-yl] diselenide showed an excellent anticancer activity and low cytotoxicity toward noncancer cells, suggesting that this diselenide is a potential lead compound for anticancer therapy.