Tobacco taxation is the most effective measure to reduce cigarette consumption and consequently improve public health outcomes. It is also an important source of government revenue. The presence of an illicit tobacco market diminishes the public health and fiscal gains of cigarette levies by making cheaper non-taxed cigarettes available. To date, the research on the extent of illicit tobacco trade in the Philippines, despite its potential to inform policies for controlling the supply of illicit cigarettes, has been limited. This study provides an estimate of the size of the illicit tobacco market in the Philippines from 1998 to 2018. It employs gap analysis comparing an estimate of the survey-based adult cigarette consumption with legally sold cigarettes in the Philippines. The illicit trade estimates are contrasted with the evolution of tax changes. The results show that the illicit cigarette market share dropped by 42% from 2003 to 2008 and by an additional 79% from 2008 to 2013. In spite of the large tax increases by the Philippine government through the Sin Tax Law starting from 2013 until 2018, the illicit share in 2018 remains similar to its 1998 level of 16% of the total market. Hence, our study finds no evidence of a positive relationship between tobacco taxes and size of illicit cigarette market in the Philippines.