Tanzania recently changed its antenatal care (ANC) guidelines to reduce perinatal mortality and improve the experience of pregnancy care. The new guideline recommends increasing the number of ANC visits from four to eight and introducing one routine ultrasound scan, among other recommendations. We estimated the budget impact of implementing the new guideline compared to the previous focused ANC guideline at public dispensaries and health centers. In a dynamic Markov model, we prospectively followed annual cohorts of between 2.3 and 2.6 million pregnant women who will be attending ANC at dispensaries and health centers for 5years. We allowed a population of pregnant women into the model every year and women exit the model at delivery. We calculated the cost of medicines, medical supplies, and laboratory supplies required to produce services from a public health system perspective. Our model neither estimated condition-related costs nor health effects. The budget impact was calculated as the difference in the estimated costs between the two guidelines. We conducted scenario analyses to explore attending more visits and different assumptions to calculate the target population. We estimated that implementing the new ANC guideline would have a cumulative budget impact of around US$154 million over 5years. The budget required will increase from US$137 million under the focused ANC guideline to US$291 million under the new guideline. Laboratory supplies will consume 47% of the estimated budget under the new guideline. We expect the annual budget impact to be US$38 million in the first year of implementation and US$32 million in the fifth year. We assumed that by the fifth year, 82% of all pregnant women would have had four or more visits. The budget impact would increase to US$214 million, with the proportion of pregnant women attending four or more ANC visits reaching 90% within 5years. Scaling up the implementation of the new ANC guideline at public dispensaries and health centers may substantially increase the supplies required to produce ANC services, particularly laboratory supplies. Studies on the health impact of the new guideline are warranted to estimate the value for money.