Benzimidazole derivatives have attracted a significant attention in recent years because of their medicinal applications as antiviral, antiulcer, antifungal, antihypertensive, anticancer, and antihistamine compounds. The one-pot synthesis of benzimidazole derivatives via oxidative condensation of aromatic aldehydes with o-phenylenediamines under mild conditions was successfully accomplished using a cobalt(II) supported on mesoporous silica-type material. The supported cobalt catalyst could be easily recovered after reaction completion and reused seven times with an excellent durability and without any noticeable loss in activity.