The structure of the Australian banking sector is similar to that of an oligopoly, which poses the risk of minimizing competition. The structure, performance and conduct of banks are important as they ensure they act competitively, however in Australia the market is dominated by four large banks which threaten the competition. The structure of the Australian banking sector is quite oligopolistic, decreasing the amount of competition evident in the market. The performance of dominant banks showed an increase in profitability and return on assets compared to international banks in a freer market. Through minimal competition, industry conduct has declined slightly with increased tariffs and investigations into possible collusion. The structure, performance and conduct paradigm of the Australian banking sector threatens the competition evident in the market. Within an industry that has a highly concentrated structure, the conduct of the parties involved tends to initiate anticompetitive behavior, which improves the company's performance. Competition can be measured within an industry using various methods, the first being the concentration rate which is the percentage of market share held by the largest companies within an industry (Young, P 2014). The second measurement tool is the Herfindahl-Hirschman Index (HHI), which calculates the percentage of market share held by all companies within an industry by taking the square root of the market share (Bikker, J & Haaf, K 2002). Banking structure can also be determined through market segmentation, product differentiation, barriers and diversification. Of the 54 banks in the Australian banking sector, the market is dominated by just four, taking up 76%... half the paper... preventing smaller and less prominent companies from being able to compete fairly in the Australian banking sector. industry.The Australian banking sector is quite oligopolistic, which has minimized the threat of competition from smaller companies. The structure of the four dominant banks in the sector has seen the introduction of anti-competitive behavior which has targeted smaller businesses. This in return has seen banks' performance increase profits and asset returns, pushing Australia to have four of the eight most profitable banks in the world. The performance of the banks has seen conduct become less competitive with the introduction of multiple commissions and expenses borne by consumers, due to the non-competition of the markets. Therefore, the banking sector in Australia has four very dominant companies with defined control, which limits competition in the market.