Nowadays the internet has brought drastic and significant changes in all aspects, especially in the dynamics of business development. With online ads carried out by Tiket.com, it is expected that brand image of its services will also increase. Along with increasing brand image after seeing promotions from online advertisements conducted by Tiket.com with the promos that have been provided, it makes tourists want to make purchase decision on Tiket.com. The effectiveness of online advertising is an important factor to support the image of a brand which can lead to purchasing decisions on a product or service. The research method used is quantitative with structural equational model techniques analysis using SmartPLS 2.0 software. The study results showed that contribution of Advertising Effectiveness directly influenced Brand Image was 81,22%. The remaining 18,78% was influenced by other factors that cannot be explained in study. Then contribution of Advertising Effectiveness and Brand Image simultaneously influenced Online Purchasing Decision was 87,59%. The remaining 12,41% was influenced by other factors that cannot be explained in study. It can be concluded that Brand Image has roled as mediator between Advertising Effectiveness and Online Purchasing Decision, because indirect influence was greater than direct influence.