Literature, internet, and museum resources were surveyed for information on nonindigenous species in the greater Tampa Bay ecosystem, Florida. Field surveys were also conducted for confirmation of some species. The greater Tampa Bay ecosystem is here defined as coastal marine and estuarine waters from Anclote Keys to the southern end of Sarasota Bay, including Tampa Bay and all marine-influenced tributaries. Sixty-five species are discussed in detail. Of these, 41 species are known to occur in the greater Tampa Bay ecosystem, nine species are suspected to be present but not well documented and 15 species are potential or expected invaders from nearby ecosystems. Of the species known or suspected to be present, 12 are cryptogenic in origin. Well-studied groups, including mollusks, chordates (fish and sea squirts), and crustaceans make up the majority of the known invasives. It is probable that continued field surveys would reveal many more nonindigenous and cryptogenic species, particularly among the smaller invertebrates. Known or suspected invasion vectors for invasion of these nonindigenous species include: shipping (ballast water, hull fouling, wet cargo, etc.), fisheries and aquaculture (bait, fishery enhancement, aquaculture escape) and private releases. Many invasions occurred decades or centuries ago, and the modern importance of these vectors is unknown. We recommend two actions. First, a formal rapid assessment of nonindigenous species in the greater Tampa Bay ecosystem should be conducted. A rapid assessment is a cost-effective means to rapidly expand our database on nonindigenous species in the area, and will help resource managers decide how to allocate funds towards research on impacts from biological invaders. Second, a formal investigation of the importance of different vectors for biological invasion to the region should be undertaken. Such a study is essential for managers and regulators when allocating resources to limit new biological invasions.