In this paper we study fertilizer subsidy schemes in Tanzania from 2003/04 through 2015/16 to better understand the key factors that led to the design and reform of various fertilizer subsidy programs in Tanzania over time and to serve as a case study to test the hypotheses from the Kaleidoscope Model of the key drivers of agricultural policy change. The analysis is based on a combination of key informant interviews and secondary literature. Focusing events played a key role in getting fertilizer subsidies on the policy agenda in Tanzania: a drought in 2002/03 was a key factor in the return of fertilizer subsidies to Tanzania in 2003/04, while the international food price crisis of 2007/08 was a key factor in Tanzania scaling up an existing pilot fertilizer voucher scheme into the large-scale National Agricultural Input Voucher Scheme (NAIVS) in 2008/09. A second key factor that put a large-scale subsidy approach on the agenda (NAIVS) was the support of powerful advocates including the President.