Farming systems provide information about the complexity of agriculture at the household level in a region. In Temanggung, Indonesia, the Java Arabica Sindoro-Sumbing (JASS) coffee intercropped with tobacco and vegetables provides an interesting interaction study. Despite its potential, no in-depth research has been conducted on farming systems and the level of good agricultural practices (GAP) adoption in JASS plantations. This study sought to analyze farming systems and determine the level of GAP adoption by the JASS coffee farmers in Tlahab, Temanggung, Central Java Province. One hundred fifty-eight purposively sampled farmers were interviewed in depth. The study employed agrarian system diagnosis as tool for analyzing farming systems, and calculated GAP adoption using the chi-square test. Before 1999, the simple farming system consisted of planting tobacco and red beans during the dry season, switching to corn during the rainy season, and keeping livestock for emergency savings and manure. However, erosion was a major problem because few wood trees existed. Farmers grew JASS coffee in large quantities and positioned it as a conservation plant and as a new income source. After 2000, they grew JASS coffee alongside tobacco and red beans during the dry season, followed by more diverse cropping during the rainy season. The study classified the JASS coffee farmers as specialist, rainforest, and diversified coffee farmers. Plant spacing and intercropping had more than 75 percent adoption rate, water and soil conservation, along with growing shade trees, had 30 to 50 percent adoption, while fertilizing and pruning had less than 25 percent. Specialist coffee farmers dominated the practice of GAP cultivation and had higher yield and income from coffee cherries than two other types of farmers.