Humpback (Megaptera novaeangliae) whale watching off Sydney, Australia, has recently seen significant growth in both the commercial and recreational sectors. Concurrently, more commercial operators have extended the period during which they conduct commercial whale watching to include the migrations both to and from the breeding grounds. This means that more frequent whale watching now occurs from May to November each year and focusses on all age classes, including calves. In Australia whale watching is managed through regulations designed to control the behaviour of vessels around whales. This study compared commercial and recreational vessel compliance with key features of the whale watching regulations between two years, 2007 and 2010, and found varying but regular breaches. Low compliance, with its concomitant increase in risk of harm to whales, risks undermining the ability of the regulatory framework to minimise impacts on whales. Whale watching regulations need to go beyond developing rules for boat behaviour around animals and consideration should be given to how those rules are enforced and whether additional management measures, such as operator permits, should be required across the industry.