Smallholder rice farming is central to poverty reduction, food security, and rural development in the Philippines. Currently, rice affordability is threatened by the country's protectionist approach to rice imports and low production efficiency. One key issue is that around 41 percent of the country's irrigable land is not irrigated. Moreover, many irrigation systems are suggested to be poorly managed with unequal water distribution. The Irrigated Rice Production Enhancement Project (IRPEP) was implemented in three regions (VI, VII and X) of the Philippines between 2010-2015. It was designed to improve rice productivity and smallholder livelihoods by strengthening canal irrigation infrastructure of Communal Irrigation Systems (CIS), improving the capacity of the Irrigators' Associations (IAs) that manage the CIS, and offering complementary marketing support, Farmer Field Schools, and emergency seed buffer stocks. As the government provides FFS and buffer stocks to farmers across the country, we focus the assessment on the irrigation and marketing activities only. We define the impact indicators based on IRPEP's theory of change, which maps the inputs and activities of the project to outcomes and impacts through various channels. The analysis is based on quantitative data from 2,104 households and 113 IAs covering beneficiary and non-beneficiary groups, along with qualitative data from project and IA staff. We estimate IRPEP's impact by comparing beneficiary and non-beneficiary households and IAs using statistical matching techniques to ensure a clean and unbaised comparison. We then use the qualitative data to try to identify the underlying factors that shaped the results. We particularly focus our analysis on regional heterogeneities in impacts because of the considerable differences between the three project regions. The main difference between regions stems from their varying levels of exposure to extreme weather events (e.g. super typhoons), as Region VIII, and to a lesser extent Region VI, experienced significant extreme weather damage during the project's implementation.