The status of Common Terns (Sterna hirundo) breeding in Canada is presented, with abundance trends in regions where data allow. Large (>12,000 pairs) concentrations of Common Terns nested in coastal Newfoundland, long the Gulf of St. Lawrence coast of New Brunswick, and in lakes Winnipeg, Winnipegosis and Manitoba in Manitoba. Nest numbers increased in the four provinces of Atlantic Canada ( 31%; 1973–2010), the Mingan Archipelago National Park Reserve Canada (MANPRC) in the Gulf of St. Lawrence ( 81%; 1986–2009) and possibly in Great Slave Lake ( 10%; 1988–2010). Nest numbers declined (-41%; 1976–2009) in Canadian waters of the North American Great Lakes. Based on recent census data (1999–2010), the number of Common Terns breeding in Canada was estimated at between 82,000–89,500 pairs, with possibly thousands of additional pairs elsewhere in Canada that have never been systematically censused: Manitoba, Saskatchewan, Alberta inland areas of eastern provinces and the boreal forest. Recommendations are that Common Terns be censused in these areas with protocols established for the Great Lakes and annual management be implemented at sites on the Great Lakes earlier identified as “high priority”. Adoption of these recommendations would achieve better understanding of national abundance trends and inform future consevation initiatives.